An intro to Skirmisher (As of 1.5.3)

Skirmisher is a class with some interesting tactics and skill trees. This fairly comprehensive guide covers the ins and outs of each tree, and also touches on races, prodigies, and general strategies.

Intro

IMPORTANT!! This guide is very outdated, there have been many balance patches since it was written. This is more a time capsule than useful advice nowadays.
I recently beat the game with a skirmisher[te4.org] and noticed there were no guides for it up on steam, so I decided to write one. This guide is by no means definitive, and contains a lot of speculation. I wouldn't rely on it if you're in a difficulty higher than Nightmare.

Why Play Skirmisher?

Skirmisher is a class that wields a sling and a shield and has good mobility. It also has nice targeted damage on its called shots. This sounds fine, until you realize that archer also has options to wield a sling and a shield, better mobility, more damaging talents, more access to a variety of debuffs, and an actual talent called... called shots.

So really, why in the ever-burning name of our dark god would you play skirmisher?

There are a few things that skirmisher has that no other class does. The first is the Tireless Combatant Tree. This tree made me average 15 stamina regeneration per turn late game. That's enough to gain stamina on the average turn if you do nothing but cycle through all of your active attack talents whenever they come off of cooldown. You also get a reasonable amount of life regeneration and eternal warrior.

Eternal warrior and the life regeneration make skirmisher surprisingly durable. There are more details in the section on the tireless combatant tree, but in essence it makes your health pool much deeper than the raw hitpoint value and light armor would normally suggest.

The combination of durability and reasonably damaging abilities with near-infinite spam potential makes skirmisher excel in drawn out fights. As long as you can find a way to avoid a fast loss, you're probably going to win.

Skirmisher also has a pretty interesting playstyle. With most classes I almost never end up using their generic attack ability past level 20 or so, but skirmisher's skill trees are made almost entirely of passive talents and sustains. Even If you never use a basic attack when another attack talent is off cooldown, you're going to spend about half of your turns using basic attacks. All of your important active skills can fit on the bar in the bottom of the screen, and playing the class well seems to be based on mastering the art of carefully weaving in and out of obstacles to break line of sight from ranged foes while desperately trying to slow the advance of the inevitable horde of melee opponents. It's an endless series of daring escapes and tightly-executed tactical maneuvers and oh-wait-did-I-actually-just-kill-the-master-with-this-how-did-I-even-do-that moments.

Skirmisher probably isn't the strongest class you can play, but I had a lot fun getting into absurd situations with this build and I hope you will as well.

Unlocking Skirmisher

Warning: spoilers ahead! Skip this section if you like discovering unlocks on your own.

You unlock skirmisher by making a counterattack at sufficient range.

Skirmisher is one of the easier unlocks in the game; it doesn't require you to be able to get a character very far, and the playstyle is also simple enough for a new player to be able to handle it. Even better, the character you need to make to unlock skirmisher can be a decent build in and of itself, if you dislike the idea of wasting time on the unlock.

Obviously, you should play a class that has a decent ranged attack early game and can use a shield. The most obvious choice here is an Archer. As Archer doesn't require an unlock itself, this is a nice choice for beginners. Unlock Agility, find a shield and a sling, then block and shoot.

The other easy choice is Sun Paladin, if you have it. Go sword-and-shield, and then block a skeleton archer before using Wave of Power on it. I ended up doing this accidentally, it's not terribly difficult.

Skeleton archers are generally the enemy of choice for this unlock, as they won't kill you if you fail it for some reason and need to try a lot of times in a row.

I hope that lack of immediate access to skirmisher won't prove a reason for you to decide to not play the class. The unlock really is pretty simple, and the class itself is pretty fun.

Buckler Training

Buckler Expertise

This ability is handy occasionally, but you really don't get into melee enough to make it worthwhile. I spent 3 points here, but one is probably sufficient.
Verdict: 1/5.

Bash and Smash

A lovely one-point wonder. Knock your opponent away with a shield bash, and follow up with a high-damage sling attack. The knockback is nice, and is does a hefty chunk of damage to boot, especially after you max buckler mastery. This ability is enough to kill roughly half of all enemies that manage to close to melee in one shot.
Verdict: 1/5.

Buckler Mastery

Deflect projectiles. Most of the attacks you'll be taking are from ranged foes, and many of them are projectiles. Further, if you max this the shield bash from bash and smash becomes an automatic critical.
Verdict: 5/5.
A brief note: This skill is bugged. It deflects projectiles when enemies shoot them instead of when they hit you, like it says in the talent description.This leads to a lot of weird effects, but the most important ones are:

• This ability doesn't trigger counter shot on deflection Edit: I did some source diving and the actual cause of this bug is that unlike Buckler Expertise, this ability never calls Counter Shot's doCounter function. It's still an issue, though.
  
• You know in advance whether it will deflect any given projectile, and can plan accordingly (and save uses of tumble)
  
• The ability will generally end up redirecting projectiles into a wall near the originator instead of into a foe
  
• The 'within range x' on the ability seems to be completely nonfunctional

Counter Shot

The ability currently only triggers on melee blocks (which includes thrown daggers, incidentally), presumably for the reason described above. Since you almost never get melee deflections, this ability is nearly useless. Further, when I actually got a chance to counter attack a foe that was using daggers the sling bullets travelled at a speed of 1 square per round. I'm not sure if that's how this always works, or if the opponent had some ability up that was slowing projectiles.
Verdict: 0/5.

Skirmisher - Slings

Sling Supremacy

Make all of your attacks deal more damage. Level this as fast as you possibly can.
Verdict: 5/5.

Swift Shot

A lovely little attack that does decent damage and takes very little time. Beware: unlike your called shots, this attack has a slow projectile speed and won't ignore enemies between you and your target.
Verdict: 1/5 to start, level it to 3/5 when you have spare points.

Hurricane Shot

Your only native aoe. Unlike other rain-of-projectile aoe abilities, this one consumes a charge of ammunition for each attack it makes. Practically speaking, this means approximately half of your total ammunition. It also has an absurdly high stamina cost for the early game. I personally left it at 1/5 and used it twice before I got poisons, at which point it got a whole lot better.
Verdict: 3/5, eventually.

Bombardment

This talent has a lot of potential, but it needs a lot of support. If you want to run this, you're going to need to shape your build around it. At the very least, you need Highborn's Bloom or hidden resources. This talent eats 75 stamina per use of shoot, and even skirmishers can't really afford that. Secondly, you need to capitalize on the additional attacks somehow. If all you're getting out of this is a small increase in shoot damage occasionally, it's not worth it. The class itself has no real built-in way to capitalize on this except for applying lots of stacks of poison. If you want more, you're going to have to look at weapon egos. Consider the following:

• The Recursion ego on a sling gives you a chance to shoot again on-hit. Importantly, the shoot you get also has bombardment applied. This is probably the most important ego to look out for, and it has an arcane power source. This, then, implies that you should really NOT go antimagic.
  
• The Thought-Forged and of Torment egos on ammunition give your attacks a chance to cause debuffs.
  
• The Psychokinetic and of Wind egos on ammunition give your attacks a chance to deal knockback.

If you decide to go this route, your attacks with 10% recursion will each be 3 attacks, with each sub-attack basically being 1.3 attacks, for a total of ~4 attacks per shoot, and 5 attacks per turn, each at ~50-55% damage. That actually sounds pretty nice, but be aware of the fact that:

• You will have to get more ammo somehow during the bombardment, probably by switching shot bags
  
• The bombardment will only last 6 or 7 turns (the duration of hidden resources or higborn's bloom, respectively, +1)

Verdict: 0/5 or 5/5.

Tireless Combatant

This tree is somewhat odd because it uses will as the prerequisite stat. Levelling will eventually isn't necessarily a bad thing (see the stats section for more detail), but you really want to max dexterity and cunning first. This means that if you want to make any meaningful progress through this tree in the early or mid game you're going to have to stock up on will-enhancing items. This gets somewhat complicated when you also want to stock up on extra pouches of ammunition and lightning/fire resistant gear as well, so I recommend not bothering to try to get more than 1 or 2 points in breathing room early, until you no longer need to carry lightning resist stuff for urkis at the very least.

Breathing Room

Get a fairly significant stamina boost whenever you're not standing next to an enemy. Your stamina costs per turn don't actually fluctuate that much throughout the game. They basically hit their maximum when you level Sling Sniper to 3. This means that levelling Breathing Room early is actually pretty useful. Getting it up to 3 at low character levels will noticeably improve survivability as well, even though the healing drops off a bit in the late game.
Verdict: 3/5 when convenient, 5/5 eventually.

Pace Yourself

Lower fatigue at the cost of global speed. You're wearing light armor anyway, so your fatigue is already hovering around 0. You're here for the rest of the tree.
Verdict: 1/5.

Dauntless Challenger

Get stamina and life regeneration based on the number of enemies in sight. You like stamina and life regeneration and you need them more when there's lots of enemies, so you like this.
That said, as long as you've levelled breathing room a bit this isn't a huge priority. Eternal warrior is.
Verdict: 1/5 to start, 3/5 eventually.

Eternal Warrior

Now, at first glance eternal warrior looks like a worse version of thick skin. It is. It's also one of your best abilities late game. The natural question here is why? The effects of resist all can be summarized as follows:
Your effective health pool is (1/(1-resist_value))*your_actual_health_pool. If you resist one third of all damage, enemies need to deal damage equal to one and a half times your base hit points (before resistances) to kill you.
All healing you receive is multiplied by the same amount. For every hit point you restore with 50% resist all, your opponents need to deal two points of damage (before resistances) to negate it.

In other words, we can get a nice measurement on the relative effectiveness of various levels of resist all by looking at the effective health and healing multiplier it bestows: (1/(1-resist)). If we start be converting to percentage points (so the new formula is (1/(1-(resist/100)))) and then take the derivative with respect to resist all value, we get dMultiplier/dResist= (1/100)*(1/(1-(Resist/100)))^2.
In other words, the effectiveness of each new point of resist all is proportional to the current multiplier squared.
Another way of looking at it is to compare the effective multipliers of someone with thick skin (15%), versus someone with thick skin and 5 ranks in eternal warrior (30%).
The multiplier in the first case is 1.17. This is pretty useful, so it's no wonder that practically every late game build maxes thick skin. The multiplier in the second case is 1.42. The difference between the two is .25. In other words, the additional benefit that you get from eternal sentinel after maxing thick skin is about 150% more than the benefit of just maxing thick skin.
Where the difference really adds up, though, is when we consider how it looks after each of the above cases use a wild infusion for 30% resist all.
Someone with maxed thick skin and an additional 30% resist all from a wild infusion has a very respectable net multiplier of 1.8. With eternal warrior on top of that, the bonus goes all the way up to 2.5. The additional 15% resist all you got from eternal warrior is worth almost as much as thick skin and the wild infusion combined were worth for the other person.
In my last game I had a physical/mental wild infusion that gave 29% resist all for 8 turns, and a bit less than 1500 max hp. While the wild infusion and eternal warrior were up, I had an effective health pool of ~3600. A normal character (maxed thick skin, same infusion) would be about that durable only if they had a maximum life pool (or normal life pool plus shields) worth 2000. Even then, I still had an additional 70% absolute healing mod on them.
Verdict: 5/5 this is one of the only real unique advantages that skirmisher gets.

Called Shots

This tree is your bread-and-butter in combat. Low cooldowns, high damage, high travel speeds, debuffs, and the ability to bypass other enemies make these talents your tool of choice for taking out high priority targets.

That said, there is a bug that I've noticed a lot that makes these less reliable than you'd prefer. Namely, sometimes you use the ability and it does literally nothing but take a turn, start the cooldown, eat stamina, etc.. This only happens when the enemies move, but unlike normal projectiles it can happen when they move in any direction-even towards you. My guess is that something in the code that makes these ignore other enemies makes them ignore every square in between you and your target, and that if your target moves during the travel time it can end up moving into one of the 'ignored' squares and have the attack bypass it. This isn't so bad when you're fighting normal enemies, but it really sucks when you miss, say, a noggin knocker on a boss (which is a thing that happened to me. It hurt. A lot.). I'd estimate that this happens maybe 5% of the time.

Kneecapper

A cheap attack that deals decent damage and greatly impedes the target's movement. This is basically a one-point wonder, but you can drop in an extra point or so if you want to up the damage.
Verdict: 1(+)/5.

Kill Shot

A rather expensive single target nuke that gets increased damage at long range. This is actually pretty bad early game, because it eats a lot of stamina and the range multiplier isn't very good until you get a sling with a range of 9 or 10. Late game, I was one-shotting wyrms. Drop one point in here for the rest of the tree early, and come back to it once you get a more robust stamina pool and a better sling.
Verdict: 1/5 early, 3/5 mid game.

Noggin Knocker

A cheap attack that hits three times, does a decent amount of damage and stuns. Note that the stun duration doesn't actually increase with talent level; it caps out at 3. Levelling this only increases the damage, but since your called shots are actually your primary damage tool that's still pretty good.
Verdict: 3/5.

Sling Sniper

Give all your called shots better crit rate, crit damage, cooldowns, and physical penetration. You like your called shots, and you like those benefits.
Verdict: 5/5.

Poisons

Should I unlock poisons?

Yes. Poisons should probably be your first unlock, actually. You'll definitely want them by the time you're clearing the Prides.

Why, you ask? Because poisons are your best source of aoe. Toxic death at level 2 and volatile poison together are actually enough to clear entire swarms of enemies via chain reaction. Start by getting on a stack on all the targets in the front, using swift shot for extra applications and kneecapper to cause a bottleneck if necessary. Then go through and kill the lowest-health enemy repeatedly. The pace of death accelerates dramatically until the last few generally die without you even hitting them directly. Hurricane shot can be used to speed up the process if desired.

Poisons also offer a sorely-needed opportunity for additional debuffs beyond your weapon egos and called shots.

Apply Poison

Allows you to poison your weapons. Further levels increase poison chance and damage. The poison chance is a pretty vital component for the entire tree, the damage not so much. In either case, you hit pretty strong diminishing returns after the first two or three points, but you'll probably want to max it or get close to maxing it eventually anyway.
Verdict: (2-3)/5 early, (4-5)/5 late.

Toxic Death

Poisons spread in a burst on victim's death. Levels increase the radius, but not by much (the third level literally does nothing). I felt so bad about that third level that I never took it, and it actually worked out fine.
Verdict: 1/5 at first to get access to Vile Poisons, 2/5 afterward.

Vile Poisons

The most important part of the tree. You really want volatile poison, so you're maxing this.
Verdict: 5/5.

Venomous Strike

A handy utility talent with a variety of effects depending on your active poisons. A point or two early-ish will give you some extra options in combat, and more later will make sure the effects stay relevant.
Verdict: (1-2)/5 early, (3-4)/5 eventually.

Trapping

WARNING: RAMPANT SPECULATION AHEAD
I didn't actually take traps, so this is entirely theorycrafting and may not have as solid a grounding in reality as I would like.

Should I unlock Trapping?

Probably not. You only really have enough class talents points to do one additional tree justice (unless you're playing Cornac, in which case I guess you could make the attempt), and poisons fit your playstyle far better than traps do.
Consider:

• Poisons have a range exactly equal to your existing weapon range.
  
• Poisons work automatically during the course of normal combat.
  
• Poisons provide a lot of additional benefit to Hurricane Shot.
  
• Poisons deal a very significant amount of damage over time. Since you tend to draw out fights, this amounts to a lot of damage.
  
• Leeching poison represents a pretty big amount of free sustain - this is especially important if you're not going antimagic and so lack access to the fungus tree.

In contrast:

• Trap ranges max out at 5 squares
  
• Deploying traps takes a turn
  
• Traps generally do far less damage than poison over the course of the fight
  
• Traps offer zero sustain

That said, if you do choose to unlock traps, here's my best guess as to how you can level and use them effectively.

Trap Mastery

Get access to more traps, and make all traps more effective. The flash bang trap actually offers some unique benefits (aoe blind and daze), so I think you want to get access to it.
Verdict: 4/5.

Lure

Draw enemies into the perfect position for a kill shot, trap, or both. Also has the possibility of getting them to waste turns and/or important cooldowns. This is a lovely ability, I would level it until diminishing returns make it not seem worthwhile.
Verdict: 4/5. Probably.

Advanced Trap Deployment

Deploy traps at range. This maxes out at a range of 5, which doesn't seem that worthwhile. Maybe one or two points lets you set traps up far enough away that you can keep people out of melee combat.
Verdict: 2/5.

Trap Priming

Primed bear traps and flash bangs seem alright.
Verdict: 1/5, or however far you need to go to get primed flashbangs.

Combat Training

Summary

Combat training. Everyone has it, you know the drill.
You want a single point in heavy armor training for the expanded selection of accessories, several points in light armor training for the fatigue reduction and defense bonus, and maxed combat accuracy and thick skin.

Thick Skin

Resist: all is good. You want as much as possible.
Verdict: 5/5.

Heavy Armor Training

One point will give you access to heavy gloves, boots, and headgear. That's a lot of extra options, so you want that. Additional points are extraneous, as you won't be wearing heavy body armor and you get access to shields via buckler expertise.
Verdict: 1/5.

Light Armor Training

The lower fatigue, better defense, and extra hardiness are all pretty nice. There are some serious diminishing returns, though, so I'd stop before maxing this.
Verdict: 3/5.

Combat Accuracy

Hitting things is important, and slings ensure that spare accuracy isn't wasted.
Verdict: 5/5.

Weapons Mastery

You don't use any of these.
Verdict: 0/5.

Dagger Mastery

It would probably be possible to use daggers sort of effectively on a skirmisher. Poisons and Scoundrel both work just as well with daggers as they do with slings, and you have the right stat distribution. None of this changes the fact that you're still more effective shooting things at melee range, and you'd rather not be in melee at all.
Verdict: 0/5.

Mobility

I would probably call this the iconic skirmisher tree, if archer didn't get it too. Disengage and Tumble are the reason why you're playing a skirmisher in ToME instead of a turret in a tower defense game.

Disengage

A cheap talent that lets you move several spaces away from a nearby enemy, then get a modest movespeed boost that lasts for a few turns or until you do something other than moving. This ability is nice for two reasons. The first is that it pretty consistently gets you out of melee range and keeps you out of it for a couple of turns while you recover stamina. The second is that both the initial withdrawal and subsequent moves trigger a reload. Generally, if you use this talent and then spend a turn or so moving you should almost completely refill your ammunition. Additional talent points increase the initial distance and make the movement buff more powerful.
Verdict: 3/5.

Evasion

A somewhat expensive instant defensive boost. It's a fine ability, but I rarely felt like I was in a situation where using it was helpful (The exception being duels with rare archers).
Verdict: 1/5.

Tumble

My new favorite talent. Instantly move to a spot within range and line of sight, for the price of a moderate initial stamina cost and a stacking debuff that makes talents in the Mobility tree significantly more expensive for a long duration. Additional talent points increase the range, decrease the cooldown, and make the debuff do less and wear off faster. I never regretted spending a point on this skill, but you still don't want to go too overboard early on when you have low stamina reserves and regeneration.
Verdict: 2/5 initially, (4-5)/5 later.

Trained Reactions

Spend a bit of stamina to reduce the damage of massive attacks. It rarely triggered, and when it did it didn't really feel like it helped very much. That said, I think it saved my life once. Worth a point or two, but don't go overboard- it's generally better to invest in the earlier talents a bit more so that these situations don't come up as often in the first place.
Verdict: 1/5.

Survival

This is a pretty standard tree. All of the abilities are pretty handy to have at least one point in. I recommend you do just that.

Heightened Senses

See traps and stealthy/invisible people. It's a handy skill, but it doesn't scale exceptionally well past the first point or two.
Verdict: 1/5.

Device Mastery

Use item abilities more often and disarm traps. A better player or someone more familiar with swift hands might prefer to put more points in here, but I don't really use item actives enough to bother.
Verdict: 1+/5.

Track

Technically, if you're using this properly you should never be surprised by a fireflash coming in from off screen. I'm kind of lazy, though, and the Fire Dragon Shield made rogue fireflashes pretty mundane. Also, my favorite hotkey is 'z'. That said, I still use Tracking on dangerous boss levels, like Urkis and the Master. I'm pretty sure it was the reason I managed to beat both of those.
Verdict: 1/5.

Danger Sense

A level in this gives you a better bonus to piercing sight than another level of piercing sight. It also gives you a small amount of crit dodging and a way to avoid failing saves that you shouldn't have failed in the first place. Not fantastic, but it's passive and not terrible.
Verdict: (0-1)/5.

Antimagic

Going Antimagic: the pros and cons

Pros:

• You thrive in extended fights. These fights are, coincidentally, the place where the Fungus tree really shines.
  
• Levelling will is actually a solid choice. Increased stamina capacity and access to the Tireless Combatant tree is perfectly acceptable, and really you don't have much else to do after levelling cunning and dex.
  
• Skirmisher has trouble preventing and removing debuffs. Antimagic Shield renders a lot of the more common DoT debuffs irrelevant.
  
• There's apparently a lovely T5 shield[te4.org] that gives Antimagic users 10% resist: all. That's enough to make the cap relevant, which is incredible.

Cons:

• Good slings and ammunition are ludicrously rare. There is exactly one[te4.orhttps] artifact sling above T3, and the highest-tier artifact ammo I can find a mention of is T4. Unless you get pretty lucky, you're going to have to rely on randarts from Ungrol for your weapons. It feels terrible to find an actually decent sling or bag of ammunition, only to realize that it has a single arcane ego and is therefore unusable. I was using a sky-blue T3 sling all the way until I killed Tannen, and I got my first decent T5 ammo from a vault in Gorbat Pride. This led to a memorable incident in which it took me about 8 entire bags of ammunition to take down the Old Forest's backup guardian. Slings and ammo are ridiculously rare, and hoping for AM-friendly gear turns out to be a much bigger gamble than I initially expected when I decided to kill the Orc Corruptor.
  
• Phase door runes look lovely on skirmisher.
  
• You need to park a psychoportation torque in your misc slot.
  
• Spectral Shield seems like it could be handy, but the magic requirement is basically impossible to satisfy when you're an antimage.
  
• You don't have the opportunity to try and pick up celestial/light for Providence or Stone Alchemy for profit.

Resolve

Even if you don't care for the rest of the tree, resolve is a genuine one-point wonder. Levelling resolve to 5 is also pretty good in that makes it very unlikely for your AM shield to ever go down, but that's a lot of points to spend.
Verdict: 1/5 or 5/5.

Aura of Silence

If you level this, it becomes a decent way to reduce equilibrium while also providing a much-needed non-physical debuff to use on Argoniel. It's fine if you can spare the points.
Verdict: 1/5 or (3-4)/5.

Antimagic Shield

Your license to ignore DoT effects from spells, poisons, and weak mages entirely as long as your equilibrium lasts. The effect is very good, but you probably don't need to level it quite as much as I did.
Verdict: (2-3)/5.

Mana Clash

A low-damage attack that lowers your equilibrium and gives you manaburn on all of your attacks for a few turns. I'll be honest, here-I regret levelling this instead of aura of silence. Skirmisher doesn't really do enough dps to burn the mana from bosses, and if they're not a boss you're better off just killing them instead of trying this. Aura is a much better way to deplete your equilibrium, anyway. It's possible that this gets better with heavy investment, but I'm not going to recommend taking it.
Verdict: 0/5.

Fungus

Should I get Fungus?

See the Antimagic section for a discussion of the benefits of going Antimagic. If you do go Antimagic, I recommend spending the cat point to unlock Fungus, as well.

Wild Growth

Makes your regeneration infusions last longer. It adds one round of duration per talent level, and at level 5 that basically doubles their effectiveness and lets you keep one up forever if you have two. You like extened fights, and this plus a decent heal mod means you don't even notice if you take less than several hundred points of damage in a single turn.
Verdict: 5/5.

Fungal Growth

Get a really small regeneration effect that doesn't stack with other regeneration effects when healed. You already have regeneration effects up 24/7.
Verdict: 1/5 for the rest of the tree.

Ancestral Life

Using regeneration infusions takes less time; Regeneration also restores stamina and equilibrium. This is a nice ability, but you don't really have a lot of points to spare.
Verdict: 1/5.

Sudden Growth

Heal several turns worth of your current regeneration effect. One point is enough to make get you to max hp. It's handy in emergencies, like when you're hit by a curse of death.
Verdict: 1/5.

Scoundrel

WARNING: RAMPANT SPECULATION AHEAD
Let it be known that I did not unlock this tree.

Should I unlock Scoundrel?

Probably yes, if you're not going Antimagic. Maybe not, if you're planning on picking up Celestial/Light or Spell/Stone Alchemy from an escort. In general, I found that I had enough talent points to level Mobility, Combat Training, my racial tree, Survival, Fungus, and Antimagic to my satisfaction. If you want to put more points into survival, you might want to drop one of those. If you're a Cornac, you get a bit extra. If you want an escort tree, you should drop one of those. Regardless, if you're not going Antimagic you have enough generics to spare for at least one additional tree, and this is the only other native tree you have. I will leave Stone Alchemy and Light off of this guide, because you should probably already know what you want to do with them if you're considering getting them.
In the end, this tree isn't really that great, but you have spare generic points and all of the talents are passive.

Lacerating Strikes

Attacks have a small chance of wounding the target for an additional 75% damage over 10 turns. It also causes them to lose a small amount of a turn. This is really slow damage, and it doesn't even do that much if it runs to completion. The turn loss is effectively a really minor global speed debuff as long as you focus fire on the target. Take it for the rest of the tree.
Verdict: 1/5.

Scoundrel's Strategies

Reduce the crit chance of people you hit. If they're bleeding, you get a small chance to make them forget a talent. This seems alright, but not spectacular.
Verdict: 3/5, eventually.

Misdirection

Get a small chance to dodge physical effects. This is literally the only talent you have that mitigates debuffs, and it mitigates the most common type to boot! It's a shame that the chance is so low, though. Level it until diminishing returns make it not worthwhile.
Verdict: 3/5, probably.

Fumble

Your Scoundrel's Strategies debuff gives targets a stacking chance to fizzle a talent and lose a turn. This seems good, level it until diminishing returns make it not worthwhile.
Verdict: 3/5, probably.

Escort Trees

It's possible to get access to certain talent categories by finishing escort quests. They start off locked, so you need to spend a category point to use them.
I would take Stone Alchemy or Light if I wasn't going AM.

The biggest draw in Light is Providence.
The biggest draws in Stone Alchemy are, of course, Extract Gem and Imbue Item (and the corresponding prodigy Crafty Hands).

There are probably better guides out there for how to get/build these trees, and I'm sorta tired of writing up skill trees, so I won't go into further detail here. If all of this sounds like a massive hassle to you, it's perfectly alright. Just take Scoundrel instead and forget the fact that these exist.

Races

Note: since this guide is pretty casual, I'm rating basically everything alright if it isn't garbage.

Cornac

You're not really that low on talent or category points, but you can still probably find something to do with the extra ones, and the lack of an experience penalty is very nice on normal.
Verdict: This is an OK choice.

Higher

You would take this to abuse Bombardment with Highborn's Bloom. Other than that, the T1 fits skirmisher's playstyle well, and extra sight range is quite handy. The T3 is something of a wash, though.
Verdict: The bombardment combo seems fun.

Shalore

You get some use out of the global speed, but Skirmisher is probably the least useful class for Timeless that I've ever seen. In short: you don't really have buffs to extend. The debuff duration reduction is nice, I guess, and it can extend the effect of your inscriptions, which is still pretty good, but that doesn't seem as fun, somehow.
Verdict: This is probably still one of the best options, because Shalore always is.

Thalore

Thalore get extra resist: all on their T3. I like the sound of that.
Verdict: This is an OK choice.

Halfling

Indomitable is really handy in a tight spot, and all the other ones are alright.
Verdict: This is an OK choice.

Dwarf

The T2 only works when you get hit in melee, and honestly it just feels like this race isn't doing much for you.
Verdict: This is still probably an OK choice.

Yeek

You actually take hit point damage occasionally, so this is out.
Verdict: I would skip this.

Ogre

You like infusions and crit a lot, so scar-scripted flesh, grisly constitution, and writ large seem alright.
Verdict: This is an OK choice.

Ghoul

A global speed penalty and can't use infusions. Pass.
Verdict: I would skip this.

Skeleton

You lose infusions, which hurts, but at least skeleton gets something to help deal with debuffs in the form of Resilient Bones. It seems tough, but unlike ghoul I can imagine someone doing well with this.
Verdict: I would still skip this.

Stats

Max dex, then cunning. After that, you can level a mix of will and strength. Levelling constitution is not highly recommended, but ends up being pretty ok for AM characters due to the healing mod.

Will vs Strength

Will provides:

• Maximum stamina (useful)
  
• Reduced failure rate from equilibrium (useful to AM characters)
  
• Mindpower (useless)
  
• Mental and Spell save (useless on higher difficulties, but handy on normal and mental was still good in nightmare)

Strength provides:

• Carrying capacity (surprisingly useful)
  
• Physical power (rescaled, so not very much, but your weapon damage scales linearly with effective physical power)
  
• Physical save (useless on higher difficulties)
  
• A massive damage increase if you take Pain Enhancement System

In the end, neither of these options is fantastic, but they both do something for you. I levelled a mix of both, and neither felt much stronger than the other.

Levelling stats for prodigies is not recommended. You should be able to boost your stats enough to qualify via items.

Prodigies

I'll only mention those prodigies that seem to have some potential, for brevity's sake.

Dexterity

• Crafty Hands: You want this if you went Stone Alchemy.
  
• Giant Leap: Moving somewhere within range 10 is handy, but probably not worth a prodigy.
  
• Roll With It: Get out of melee, if you have somewhere to run to. You already have the Mobility tree for this. Pass.
  
• Vital Shot: This is a decent damage single target nuke that also makes the target useless for 5 turns. You don't actually have very many active attack talents, and this is a nice thing to replace a shoot with.
  
• Windtouched Speed: 20% global speed is nice. I would consider this for your second prodigy if you go AM, but the prerequisite might be tough.
  
• Automated Reflex System: Like Tumble, but worse. Pass.

Cunning

• Eye of the Tiger: You get lots of critical hits, and 2 turns off of a 6 turn cooldown on called shots is a pretty big impact. I would consider this.

Willpower

• Draconic WIll: You struggle with cc. This prevents approximately one-third of it, probably more if you're good at timing. A very solid contender.
  
• Hidden Resources: A necessity if you want to level Bombardment without playing Higher.
  
• Lucky Day: +16 accuracy and defense, +12 crit chance, and a piddly amount of saves. The crit chance is nice, but you can do better.

Constitution

• Bloodspring: Decent, but you can do better.
  
• Draconic Body: If you get that low you're probably going to lose the fight anyway.
  
• Eternal Guard: Very good, if and only if you have a shield that can block some forms of elemental damage.
  
• Never Stop Running: The nice thing about this talent is that you reload ammo for every tile you move. I like it, but a movement infusion is probably a better choice.
  
• Spine of the World: Physical effects are the most common type, so this is pretty handy- especially because your class has no way to reduce the incidence or impact of debuffs on you. One of the top contenders, less so if you have other ways of negating some of the more potent physical effects (100% stun/freeze resist, halfling).

Strength

• Pain Enhancement System: It might be worth levelling strength just to make this prodigy better. Increases to dexterity and cunning of this scale represent a HUGE damage boost.

Magic

• Mystical Cunning: You can, technically, get poisons and traps. If you do, this seems like it could be alright. I wouldn't do that first bit, though (Unless you're a Cornac, in which case you can probably make it work).
  
• Revisionist History: Any fights you care about will last longer than this, as a rule.
  
• Spectral Shield: You need to take an escort category to unlock this, and it isn't really very useful without Eternal Guard. That said, this plus Eternal Guard is incredible and Celestial/Light for Providence removes a lot of the need for anti-debuff prodigies, and lets you qualify for this to boot.

Inscriptions

I recommend going for 5 inscription slots. You just don't have that many trees to unlock, and you also get a lot of benefit from additional inscriptions.

Wild Infusions

Do you remember the wall of text way up there in Eternal Warrior? Of course you do, now here's a quiz: how much does getting an extra 30% resist: all really do for you, anyway?
Answer: a lot.

On a completely unrelated topic, what's one of the biggest weakness of the skirmisher class?
Answer: The class has no talent but scoundrel's T3 that actually prevents or weakens debuffs, and no way to remove them once they're applied.

Wild infusions help negate a glaringly obvious weak point in your build, while simulataneously emphasizing one of the class's unique strengths.
I took two of these babies, and never looked back.

Regeneration Infusions

Thanks to your high resist: all you end up with a pretty decent effective healing mod. If you stack that with an actual healing mod and some base life regeneration from the Tireless Combatant tree, regeneration infusions let you tank an absurd amount of attacks. When you add in Wild Growth doubling their duration, two regeneration infusions become mandatory.
I still recommend at least one and/or a shielding rune even if you're not going antimagic.

Movement Infusions

Get a ton of movespeed for a few turns, then resistance to those nasty movement-impairing effects for a few rounds afterwards. These are good for a couple of reasons: You like mobility anyway, and this is better than your mobility talents in some cases because every tile you move into will refill your ammo. You'll probably go back to full capacity after using one of these. Also, your class doesn't offer you any reliable ways to avoid or mitigate debuffs, so finding inscriptions that do is very helpful.
A solid contender.

Heroism Infusions

Get a solid damage buff and buy time for some of your healing items and/or abilities to recharge. I didn't get much use out of this, surprisingly. Situations in which the negative health became relevant always ended in my death anyway. Generally, skirmishers just shouldn't really have their health be dropping very much (at least on Nightmare and below, I guess-not sure about the higher difficulties).
That said, I would probably go for something that stops these situations from coming up in the first place, or a better panic button for when they occur.

Teleportation Runes

Arguably the best panic button out there.
You'll want one of these or a psychoportation torque. Use them if your health starts dropping and you can't break line of sight.

Controlled Phase Door Runes

The major advantages these have over movement infusions are instant movement, the ability to go through walls, and a much shorter cooldown. That second bit seems incredibly handy in many of the more common maze-like maps which might otherwise see you trapped in a dead end.
A solid contender.

Shielding Runes

These would take the place of regeneration runes if you want to use them. They do have some nice advantages, such as an instant cast speed, and they get the same benefit from resist:all that a regeneration infusion does. The major downsides are that you can't improve these with healing mod, and that you can waste a lot of the benefits if you don't properly time the (short) duration to intersect with your opponents' attempts to burst you. On the other hand, if you go Celestial/Light and use Bathe in Light, the duration limit gets a bit less drastic, although you do lose the benefit of an instantaneous cast.
I can see someone making this work.

Manasurge Runes

You might need one of these if you're going Stone Alchemy and don't have any mana regen gear. I would probably swap it out before the final boss fight, at the very least.
Situationally necessary, but terrible in combat.

Weaknesses

It's very important to know your weaknesses as well as your strengths, so that you can recognize and avoid unwinnable fights, and so that you can choose gear and inscriptions in such a way that unwinnable fights become less common.

This section will contain a list of the weaknesses I have observed while playing skirmisher, and a list of all of the deaths of my winning character, along with an analysis on if and how they could have been prevented.

In short, the biggest weaknesses of skirmisher are

• Debuff vulnerability: You have no reliable ways to prevent debuffs from being applied or to remove them once they're present.
  
• Low damage output: It's a good thing you win drawn out fights, because there's no way you're ending the important ones quickly. I frequently went through multiple bags of ammunition while killing some of the tankier bosses.
  
• Reliance on physical effects: Spine of the World absolutely wrecks you, and one of the final bosses is guaranteed to have it. Good luck.

The first death: a hint of things to come

My first death was to a dreaming horror in Daikara. It effectively killed me with a single talent: Ravage. When it applied Ravage I saw instantly that my health pool couldn't last anywhere close to the entire duration, so I popped a wild infusion. Unfortunately, it only cleared the distortion effect. The next thing I tried was a regeneration infusion, hoping to tank it out. Unfortunately, Ravage cleared my regeneration infusion immediately, because that's what I get for not carefullly reading the debuff text. After that, I broke line of sight with the horror and desperately hoped that I had done the math wrong and could wait it out. I couldn't.

What can we learn from this? There are two important weaknesses highlighted here. The first is that relying solely on inscriptions for sustain is a really bad idea, because occasionally they get cancelled somehow (*cough* curseofdeath *cough*). The other is that skirmisher is very vulnerable to debuffs. I had no way to prevent the debuff from being applied in the first place, and once it was there there was nothing I could do but burn a wild infusion and hope it hit the right target. Even if you could get 100% resist to stuns, pins, dazes, and confusion, there are a couple exotic talents like this that will slip through the cracks and absolutely ruin your day. You need to have a plan for dealing with them, via items, inscriptions, escort trees, or prodigies. In this specific case, I could have been carrying two wild infusions, which would have guaranteed a clear on Ravage.

The second death: Arrogance

I had only ever fought the Grand Corruptor once before. There's a story here, and most of it is that the Spellblaze scar looked scary and I never entered it until the one other time I won the game, when I decided to give it a shot after clearing every single orc pride and backup guardian and the slime tunnels to boot. This left me with a somewhat skewed image of the Corruptor; Namely, I thought he had poor damage and was squishy. I was wrong, on both counts.

What can we learn from this? Arrogance kills.

The third death: the dark crypt

As so often happens in the dark crypt, I got surrounded. Unfortunately, I got surrounded by rares while in a bad position in the hallway (too far from either end to tumble out). I wasn't carrying a psychoportation torque at the time, and so died after a few desperate turns spent trying to thin one side enough to tumble past them. I then respawned, finished thinning that side and managed to make it out, at which point the battle became pretty straightforward.

What can we learn from this? I could have won that fight if I'd teleported away. Carry some means of teleportation on you at all times.

The fourth death: Celia's Crypt

I came up with a great plan for this dungeon: start the Rod of Recall for 20 or 25 turns in advance, then open the door and kill Celia, and then have the recall trigger before I have to deal with that massive swarm of rares in an enclosed space. Satisfied, I saved my game and went to sleep.The next day, I loaded up my game, opened the door, and killed Celia. Oops. As the horde closed in, I desperately triggered the rod and started the countdown. Then one rare teleported me into the middle of the mob. I had about 20 turns left on the rod when I died.

What can we learn from this? Intricate plans are great, but you should probably execute them correctly if you want them to work.
Also, the center of a mob of rares is not a good place to be.

The fifth death: Argoniel

I killed Elandar without too much trouble, but he managed to deactivate my AM shield before going under. Argoniel then proceeded to be immune to my debuffs (all of them are physical), immune to counterstrike, highly resistant to physical damage, and all too eager to close into melee range and hex me into oblivion. Then he hit me with a Curse of Death as a cold wyrm and its hatchlings spawned from the dragon portal.
Even after I respawned, I nearly died several more times in the ensuing fight, all of them due to Curse of Death. Thankfully, after I closed most of the portals Argoniel proved incapable of killing me on his own, thanks to a combination of high amounts of damage resistance, AM shield, and some active healing from Sudden Growth, Earthen Beads, and Bunny Hop.

What can we learn from this? Argoniel is practically tailor-made to wreck you. He ends up being functionally immune to all of your debuffs, including the entirety of the Poisons tree, and he lowers your resistances with spell shock and prevents you from regenerating life to boot. I would definitely consider stockpiling some gear specifically for this fight- stuff with active mental or magical debuffs, or that cleanses magical and/or mental effects somehow. Alternatively, a method of preventing debuffs from being applied to you in the first place would help.

Speaking of weaknesses, I'm nearly certain I got some stuff in here wrong. I'm just not sure what. If you have insights you wish to provide (politely, please!), the comments section is down there.

I hope this guide was helpful, and wish you the best of luck with your skirmishing.

[sunyattakid]

Very helpful, thanks

[VJ]

Great guide, thanks.