Best defence in the caverns.

[Tanaka Khan]

So I busted through into the caverns for the first time tonight, placed a door and wall around where I entered and figured I'd slowly start exploring. Unfortunately the beasties that dwell in the caverns had other ideas. I soon found myself defending the very bedrooms of my dwarfs from these foul beasts. While I was able to manage dealing with these invaders, I was unable to actually stop them from walking through the lower door. Yes I could have locked the door, but then that would have stopped my dwarfs from mining, gathering resources and exploring without me absolutely micro managing every entry and exit into the caverns.

So what I'm after are any tricks, ideas or really cool fortress layouts I could use to defend my fortress a lot better (the defence could also be used topside, I've been very lucky in not getting a lot of attacks, just thieves attempting to steal from me).

[Fel]

Doors are not supposed to be defenses anyway, there are plenty of creatures (even more in caverns) that can just destroy them.
It gets worse, those creatures are usually among the dangerous ones.

Just don't go for the cavern's resources until you are ready for the dangers that lurk in there.
It is relatively easy to section off a small portion with a wall (all the way to the ceiling, there are plenty of climbers or flying dangers down there) if you really need access to the caverns for some reason.
It's not like there is much in caverns that isn't also available everywhere else on the map, in a much safer way, except for the stuff that wants to eat your dwarves.
There is the silk I guess but walling off a small portion of the cave should bring you enough of it for the short term stuff like moods.

Even for the underground trees and the "moss", you can easily make some room to grow that yourself once you breached a cavern, even if you wall it off.
You will need to dig a relatively large area (several levels with the floors removed if you want the trees so start from the "top" of the space you want to allocate to it when digging), pour some water to make mud on the floor, drain it and/or let it evaporate then just wait for the moss to grow on the floor.
Trees and other plants will grow on their own on the moss, as long as you don't trample it all the time, just like for grass, plants and trees on the surface.


Anyway, what you need in order to defend against the caverns while leaving the access open is a strong military, setting their barracks as a mandatory part of the path between caverns and the rest of your fort.
Of course, the usual traps help, but the more dangerous stuff in the caves walk right over traps without triggering them anyway.
They also just destroy untrained militia and many of them are relatively hard to kill, on top of nearly always having some kind of poison, webbs or fire to use as well.


TL;DR: don't do caverns, they are bad for your dwarves (their survival at least).

[Rat]

a locked door will defend against anything coming in. If you want to have the cavern open to your fort with an unlocked door then you need military guarding it. either put their training equipment down there and have them train right in the entrance to your fort from the caverns so any creature would have to walk through them or design a patrol and have your military patrol around the entrance. I don't agree that you should avoid the caverns, there's tons of great stuff down there

[Fel]

Originally posted by Rat:

a locked door will defend against anything coming in

This part is only true because of a bug introduced in version 50 that makes building destroyers not work as they are supposed to, and anyone relying on this will have some real issues once it gets fixed (I find it weird it wasn't fixed already but then again there are bugs that have been there for years).

I would really like to know what that "tons of great stuff" supposedly in caverns are though.
Outside of vegetation (that can be easily acquired without going in them) and silk (you don't really need much of the thing and caravans can bring it as well), it's full of dangerous things.

There is a somewhat spoilery thing in the form of 3x3x3 blocks of obsidian, usually with plenty of gems on them, but I'm not sure I would count them as "great stuff" given what can be inside.

[Rat]

trees (many embarks can have zero trees on the surface, like deserts, glaciers, oceans, tundras, etc), clean water (many embarks have no other sources of water, similar to trees), silk, sand (even if your embark does not include sand when you chose it, there's almost always sand in the caverns), fishing, extremely valuable animals you can domesticate (worth on average 4x as much as farm animals you can embark with or trade for, giving you 4x as valuable leather and bones for your animal industry), metal and gems you can easily find instead of having to exploratory dig in solid rock, fertile soil, all the dwarven crops to gather if you run out of seeds.

All of this is "indoors" too so you don't have to worry about weather, which is a significant mood killer of dwarfs, especially if you're in an evil biome. I would argue anything you can get from the surface and the cavern is better to get from the cavern since it won't expose your dwarfs to rain or cave adaption sickness and they like being underground much better. this is especially true in evil biomes where it can rain blood and other nasty things on your dwarfs. Personally love the caverns for all these reasons.

[McOrigin]

Artifact doors cannot be destroyed by building destroyers even if they get ever fixed.

[Fel]

Except most of it doesn't need to be done in caverns.

Cutting a few trees is definitely helpful if your surface doesn't have any and what the caravans bring is not enough for your needs even after requesting logs to be brought.
For water, it's a fair point, asuming that you don't have any aquifer, but you don't need to go into the cavern itself, building a well to have your bucket brigade fill a pond (safer reservoir) from its water is a whole lot safer (flying stuff can still come from the well so you need to make sure to safe-guard it, a bridge and a lever to close it off when not needed for example).

Fertile soil only requires some mud, so the previously mentionned well can help with that as well.

In fact, except for valuable wildlife (that you need traps to catch unless you just plan on killing them, so just baiting them with a cat on a rope works well) and exposed ores/gems, none of it requires risking leaving a proper entrance to the caverns, walling off a portion of it (which is usually fairly easy to do safely if you don't wait until forgotten beasts pop out).

For long term access to trees and plants, making a "tree farm" is usually a better way anyway, you can make grazing areas for your animals in the same way (you would want to use a different room to not trample young trees and plants though).


Don't get me wrong, if you are advanced enough to embark in hostile places like you mentionned, using the caves is probably a decent idea, but it requires extra preparations and knowing what to do before hand, not something a relatively new player like OP would be able to execute properly early on.
Plus when you are good enough at the game, keeping some danger at hand also helps to keep things from becoming boring.
If you go to very hostile biomes but completely avoid the dangers from them, there isn't much of a point in going there anyway.

If you are knowledgeable like that, you would also know how to get surface stuff without needing to be exposed to the elements, which doesn't do much on glaciers or mountains but is helpful just anywhere else.
You can get surface crop farms, grow grass, plants and trees pretty easily at that point (again, assuming the biome supports them), which means access to a wider variety of things as well as fruit trees.


I guess what I am trying to say is that caverns are a risky place that should be handled with caution because a lot can go wrong down there.
Things going wrong is part of the game though, so you should decide knowing about the dangers and about the ways you could avoid caverns while getting most of the benefits from it anyway (to be able to make an educated choice).

[Rat]

nothing ever "needs" to be done in this game, you can seal yourself off and live in total safety with zero threats and survive off nothing but plump helmets if you wanted. that's boring though, and the caverns have tons of worthwhile stuff that I mentioned. the surface is also a risky place because of things like agitated animals, so sending your dwarves out either above or below has risks. I would rather have a military patrolling down there getting into fights with troglodytes and cave toads while my dwarfs go about their business in the caverns than just seal it off and wait for a small amount of trees to grow slowly in a farm, especially with the amount of trees I use. It's a lot more entertaining and eventful to have an automated patrol and open access than it is to micromanage and exit into the caverns and never have a threat present from them, and OP specifically mentioned not wanting to do that with a locked door which is why I suggested it

[Darzan]

I like to make military watch/training post near caverns and be very careful when and why I open gates. It is best to have 3 gates in row - 2x stop gates and one atom smasher just for case. Also my stairs have hatches on them and BD safe doors at some places for case when something get through. I consider caverns like zoo. You have be careful there but it great resource to have.