Hey, everyone. I completed the Rebalanced Campaign LASO Playlist (version 3.1.1 of the mod) and I have some tips for anyone willing to take the challenge. I'll cover general tips and tricks, as well as level-specific stuff. Let's begin.

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GENERAL:

- First of all, I used a playlist made by Halo Completionist on YouTube
( https://www.youtube.com/playlist?list=PL3bi5dIhs8VX1pfVBZXGeZvPcqTzB1EjG )
Most of what I'll talk about is covered here, but I'll warn you that this playlist is on the vanilla version of Halo CE.
This will definitely help you, but some tricks that he uses might not be doable here on Rebalanced (Example: the grenade jump to get to the 2nd floor of the shuttle bay in Truth and Reconciliation. The altered frag grenade bouncing physics mess up the timing of the jump.)


- Secondly, if you're willing to learn or already know how to perform speedrunning tricks, go ahead and do them, they'll save you a ton of time and frustration. The HaloRuns Discord has many tutorials for them, and you can access it on their website ( https://haloruns.com/ )


- This is a full gameplay of the mod, on Legendary, with most easter eggs. In some levels I'll mention them, and here you'll probably see how to do them (I won't mention all of the easter eggs, so feel free to explore the levels before playing on LASO)
( https://www.youtube.com/watch?v=A8ksJ7w2vuI )


- Most of the easter eggs are marked by a green Forerunner symbol. Increase that FOV baby


- There is a way to work around the Iron skull on MCC. As soon as you die, pause the game and hit "Save and Quit". When you're back at the main menu, go to the LASO playlist and hit "Resume". This respawns you at your last checkpoint (You're welcome).


- These 2 button combos are your blessing in this journey. They are:

1) Backpack Reloading (BPR) ---> Reload a weapon while being able to use the other (only works with magazine-fed weapons)
Press RELOAD + RELOAD + SWITCH WEAPON in rapid succession (for me, these are X + X + Y on controller). The reloading animation sounds will keep playing, and you can reuse your reloaded weapon when they finish playing.
Use this whenever you find yourself in a chaotic place and don't have the time to stop shooting foes.

2) Infinite Ammo Glitch (IAG) ---> Yes, you read it right. You need 3 weapons that you can pick up (2 on you and another on the floor).
Stand near the 3rd weapon, and then press RELOAD + PICK UP WEAPON, in rapid succession (for me, these are PRESS X + HOLD X on controller).
This starts reloading the weapon you want to conserve ammo, and drops it in the floor.
The reloading animation sounds will keep playing.
When they stop playing, wait 1 or 2 seconds and then pick up the weapon.
It is now reloaded without using the reserve ammo.
This is most effective when the magazine is completely depleted.

Pro tip: when performed on the shotgun correctly, it'll pump when the reloading is finished, giving you a visual cue. The flamethrower gives you an audio cue when reloaded, it plays a "click" sound effect

Edit: On keyboard, I found this can be performed way more consistently by pressing "reload" twice before switching weapons (for me, that is "R" + "R" + HOLD "E")

Warning: If you are reloading a weapon, but you have less ammo in reserve than a full magazine, the reloading sounds must play more than once (Example: reloading the Rocket Launcher with only 1 rocket in reserve. The sounds must play TWICE. Or, reloading a sniper with 1 bullet in reserve, the sounds must play 4 times).
This applies to ALL weapons.


- This is probably the most important topic in this entire discussion.
Each weapon in the game has a unique ammo cartridge that can give you a maximum amount of ammo per cartridge. I'll list the amount of ammo each one gives (remember that in LASO the Recession skull is on):

Sniper Rifle: 12 bullets in this mod, 16 in vanilla
Assault Rifle: 240 bullets
Pistol: 60 bullets
Shotgun: 24 shells in this mod, I don't know how much it gives in vanilla
Rocket Launcher: 2 rockets
Flamethrower: 100 ammo

If you need to, go online and look for pictures of which cartridge gives ammo to which weapon.
The playlist mentioned at the beginning shows a few of them.

Example so you understand why this is important.
Imagine you're on Truth and Reconciliation, at the shuttle bay where there are 2 Spirits docked. There is ammo for your sniper, and there won't be any extra ammo until the command room (where there's a gold elite).
The maximum amount of sniper ammo you can pick up is 4 on the magazine + 24 on reserve.
If you have 20 ammo in reserve for the sniper, and you pick up a cartridge, it'll give you 4 ammo (2 shots with Recession on). But, if you have 12 ammo in reserve, a single cartridge will give you it's maximum amount of 12 ammo (6 shots with Recession on).
After you pick up a cartridge, it disappears forever.
ALWAYS remember this tip.


- Despite the Foreign skull being on, you CAN use the Fuel Rod Cannon and Sentinel Beam (Ruby, if you're reading this, please DON'T fix this, they're the only way I could complete Truth and Reconciliation and move past the 1st room on 2 Betrayals LOL).
Just remember that their ammo will deplete VERY quickly, due to the Recession skull.


- When going against Hunters, and they're running at you, stop moving for half a second, and then evade their melee. This makes the Hunter melee slightly earlier, and gives you enough time to not be hit by them. If you just run in circles, you won't have time to evade them, as they'll melee when very close to you.


- Whenever possible, let enemy factions fight and weaken each other, less work on your end.


- In some levels, you spawn with plasma grenades on your pocket. These ones you CAN use, you simply won't pick up more on the floor, due to the Foreign skull.


- Whenever you enter a boxing match with an enemy (or enemies), choose either a weapon with a fast melee animation (i.e. Assault and Sniper Rifles), or high melee damage (i.e. Rockets, Fuel Rod and possibly the Flamethrower).


- The ODST Flood Combat Forms give you some stuff when defeated (ammo, grenades and sometimes even health packs)
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Now onto LEVEL-SPECIFIC tips:


1) Pillar of Autumn: Very straightforward level, not much to talk about. There are some extra weapons later in the level, and they are a flamethrower, sniper rifle and shotgun.
I don't know where there is ammo for the flamethrower, but you can use ir for the IAG nonetheless.
The other 2 weapons have ammo for them, but it isn't neccessarily in the same room/section of the level as the weapon itself

Edit: There are other weapons hidden throughout the level, even in the beginning.


2) Halo: In the river section, there's a crashed lifepod with a sniper, allowing you to use the IAG. Also, one of the 3 lifepod sections has a Marine with a sniper. Get him on your warthog, he'll be extremely useful.
He always enters the passenger seat, as the better the weapon a Marine has, the more likely he'll enter the passenger seat

Edit: It's also possible to get Johnson in your warthog, when you first get it.

Edit #2: There's an easter egg switch, right before crossing the light bridge, that gives you an interesting object that might be desirable...
When facing the bridge, before crossing it, go to the left structure, you'll find a switch that activates a teleporter that is a bit further back in the level.
Go to the other side, activate the 2nd switch and have fun.


3) Truth and Reconciliation: Ammo efficiency is the name of the game, remember the ammo cartridges tip. Look out for Fuel Rod Cannons (there's one in the shuttle bay with the docked Spirits, and another that a Heavy Grunt drops in the command room).

Edit: Replaying the level on Legendary showed me that the Fuel Rod Cannon isn't a fixed spawn on the spot that I found it. It can either be dropped by a Heavy Grunt or it spawns somewhere else and I blasted it towards me accidentally. I'm not sure which case it is...

Edit #2: Found the Fuel Rod spawns in the shuttle bay. One spawns in the platform in the middle platform ( https://1drv.ms/u/s!AnrptNRlK-adlE6Hn3SMrgJWKjy0?e=PCCgWF ), and another spawns with a Heavy Grunt, after you reach the 3rd floor and move halfway through it (the Grunt spawns in the door you came through)

Edit #3: After you clear the command room, and the exit door opens, instead of going to the left and into the path to the prison cells, go to the right. You'll find an overshield.

Edit #4: In the prison cell where there are no allies, but there's ammo and an active camouflage, in this mod there are 2 cells with enemies (one has 3 Grunts, the other has 2 Jackals). The enemies are harmless, they don't have any guns (but remember that the Grunts explode after death).

4) Silent Cartographer: You can skip the first beach fight entirely, but I decided to do it. It's relatively easy, since your allies are very competent. Headshot all Grunts quickly so they don't kill your allies with plasma grenades, and also their post-death explosions might kill Elites as well.
At the end of this fight, when there are 2 Hunters, don't be afraid to use the Shade Turrets, as they often get very distracted by your allies (especially because some ODSTs like to flank the final enemies).
If you do this fight, you can come back to this area after unlocking the security station and you'll find plenty of ammo.
There's an easter egg teleporter here as well. I didn't know how to activate it when I was playing, but there might be some rewards there.

Edit: If you go disable the security station, in the area right after the 2 Hunters, where there are some Grunts, Elites and Jackals, you'll go to the facility itself.
Before doing that, look for the switch, it is behind one of the pillars (look for the green symbol, the playthrough linked above shows where it is)

Edit #2: Activating the teleporter network will open teleporters inside the main facility as well, making your way out of it quicker and also safer (if you use the active camo efficiently).


5) Assault on the Control Room: On the part where you first grab the Scorpion tank, there's a group of Marines.
Usually, Johnson spawns here (with a sniper rifle).
Kill the enemies before they kill him, and get him on your tank.
This isn't as big of a deal as it was on Halo, but is Johnson with a freaking sniper. Need I say more?
*This is only the case if you don't do the Bridge Fall/Banshee Grab trick at the beginning of the level


6) 343 Guilty Spark: While inside the facility, do the easter eggs. They will spawn Sentinels in some rooms, helping you clean out the Flood. Also, one of the easter eggs activates teleporters on the final swamp area, by the big tower. On the other side, there's a sniper rifle.

Edit: on the 2nd part of the facility (when you go down an elevator after the Flood Reveal), there's a switch to spawn Sentinels that can only be used by the Engineer. If you want to save it, look for a shotgun and enter this room on the upper level.
In case you save the Engineer and it doesn't activate the switch, you forgot to press another switch, in a previous room.


7) The Library: Your best friends are the Flamethrower and the Shotgun. After the Rocket Launcher enters the party, the magical duo is Rockets and Flames.
You can do the IAG throughout most of the level, but there are some hallways with infinite spawns. Here, your only option is to run and gun. Leave your 3rd weapon behind and never stop running.

You cannot bring a 3rd weapon with you on the elevators, but this isn't a big issue, you'll find another one soon enough (on the opposite side of the elevators, there's ammo, health and guns).

Also, the easter eggs are helpful, once again.
On the 2nd floor, grab a Ghost, dodge the Fatty Floods (Carrier Forms) and book it to the elevator.
On the 3rd floor, use the Wraith and just take the time to clean everything up (be careful with the Rocket Floods).
Also, in the area where the Wraith spawns, there's an easter egg encounter, where you save an Engineer.
It'll open a teleporter to another area, where there's some health, ammo and a sniper rifle.
There are some more, happy hunting :)


8) 2 Betrayals: On the 1st encounter of the level (the Control Room), there are a bunch of Sentinels scattered across the room, but 4 spawn close to you.
Throw one of your plasma grenades at the floor near them and hope their Sentinel Beams fall near you.
Also, when facing the door, there are 2 Sentinels that spawn right behind you, so move quickly to the cover on your left (the one on the right is not fully closed, you'll see what I mean).

Later, when you reach the 2 bridges that you have to cross and are side-by-side, Ruby was kind enough to put an active camouflage on the rooms that are immediately before each bridge.
Just be careful to not be accidentally blasted off the bridges by the enemies fighting each other.

Later in the level, on the 2nd pulse generator area, there's an easter egg room (opposite to the main objective), with ammo, health and a switch that activates a teleporter.
After grabbing what you need, be careful, you'll be ambushed on the pitch black hallway by invisible flood (or a sword flood, if you activated the teleporter prior to getting the ammo).

If you choose to, you can go through the teleporter, it'll take you to the beginning of the level (in the Ziggurat), and a fight starts.
You have to protect your allies against SEVERAL waves of Flood (entering the warthog with the regular turret is very helpful, and in co-op this fight is A LOT easier).
If you manage to complete this, then later in the level (the 3rd pulse generator area), Foehammer will reward you with a Scorpion tank.

Here is the complete map for the mission, in case it helps:
https://halo.wiki.gallery/images/3/36/TwoBetrayals_Scaled-SLoftus.jpg


9) Keyes: I did the Flood Bump at the beginning of the level, which skips falling off the ship and finding your way back onboard (essentially ~90% of the level).
So, if you choose to do the level the regular way, sorry but I can't help you here.
What I remember is that right when you first fall off the ship, there'll be a flamethrower nearby. It'll be insanely helpful, both using it normally and with the IAG.


10) The Maw: At the very start, there's an empty shotgun with ammo nearby, grab it.
The fights between different enemy factions are everywhere, use them to your advantage.
Not much else to talk about here.

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I hope all of this helps you on your attemps :)
Also, share how much time it took you to complete this challenge (it took me 3 days, no lie), and also any knowledge that you learn and think is helpful. I'll keep adding info here, once I come accross it.

Happy dying :D