You cannot kill a Worm
This is the thing to internalise before you spend anything on underground defence.
A Worm is an immovable enemy that cannot be attacked or built over. Guards do nothing to it. Traps do nothing. Turrets do nothing. It sits in a hole, and when a Steambot walks past, it bursts out of the ground and swallows the bot.
There is exactly one answer: a Thumper, placed so its active range covers the Worm’s den.
And that answer has a catch that ruins a lot of runs — it only works while the Thumper stands. The moment you bulldoze it, deactivate it, or move it, the Worm pops back up and goes back to work. A Thumper is not a kill, it is a lid.
Because of that, the practical advice is to site your Thumpers and then leave them alone. Do not reclaim them for a nicer layout later.
Why Worms are the worst enemy you will meet
Every other enemy in the mine disables your bots. A disabled bot can be revived by a Mechanic. Worms kill. A swallowed bot is gone permanently, and each Worm can swallow one Steambot per minute.
Two behaviours make this manageable if you know them:
- Worms have limited reach. They can only eat bots that pass right by them. Other miners can walk past a Worm that is already chewing without any issue — the danger resets the moment the first bot is digested and it goes looking for the next one.
- Your workforce panics and flees. Guards do not. Panic costs you production time even when nobody dies.
How to spot one before it eats someone
The tell is visual and easy to miss. A Worm’s hole is a pile of dirt in the abandoned parts of the map with a glowing tentacle — a yellowish tail — waving over it. Sweep for those before you route your miners through a new area, not after.
How to unlock the Thumper
| Step | Requirement |
|---|---|
| Milestone Level 11 | Reach it by getting at least 80 Aristobots |
| How you get Aristobots | Satisfy the needs of your Engineers — this is a surface-side requirement, not a mining one |
| Armory | Build one of at least 3x3 tiles |
| Place the Thumper | Its effective range is limited, and you can see the reach while you are moving it |
Note again where the real gate is: 80 Aristobots. That is a housing-and-services target in the town. If you are getting eaten in the Marshy Ruins, the thing you skipped was on the surface.
Hives cannot be destroyed either
Hives are the second thing players try to solve by attacking, and they cannot be solved that way.
- There are two Hives in the Marshy Ruins and four in the Crackling Depths.
- There is no way to permanently deal with a Hive. You kill the swarm, not the source.
- The game warns you that an attack is imminent and tells you which Hive it is coming from, with a countdown timer.
- Digging up a Rocket Part makes the nearest Hive prepare to attack. This is the single most reliable way to get swarmed, and it is worth pre-positioning before you unearth one.
- If a Hive is within sight but has no path to your bots, enemies spawn from the nearby walls instead. There is no safe sightline.
Enemies reach you three ways: Enemy Soil (a block that collapses when exposed and spawns one), Burrows (rise from the ground and break open on their own), and Hives (timed swarms).
The Armory, sized properly
The Armory holds four machines and its capacity is purely a function of its footprint:
| Armory tiles | Machines | Money | Sheet metal | Plastic |
|---|---|---|---|---|
| 9 | 4 | 3,150 | 9 | 9 |
| 11 | 5 | 3,850 | 11 | 11 |
| 13 | 6 | 4,550 | 13 | 13 |
| 15 | 7 | 5,250 | 15 | 15 |
| 17 | 8 | 5,950 | 17 | 17 |
| 19 | 9 | 6,650 | 19 | 19 |
| 21 | 10 | 7,350 | 21 | 21 |
| 25 | 12 | 8,750 | 25 | 25 |
9 tiles is the minimum to build anything at all, and it hands you 4 machines immediately. Every 2 tiles after that adds 1 more.
For sizing: with 10 to 15 Guards on balanced difficulty, aim for 21 to 25 tiles. That covers a Thumper for the Worms plus real defences at the Hive spawn points. 41 tiles gives you room for 20 machines, which is overkill unless you want to stop watching the mine.
The four machines
| Machine | What it is for |
|---|---|
| Thumper | The versatile one. Suppresses Worms, and also slows and damages anything approaching. The only anti-Worm tool. |
| Flame Turret | Durable, ignites groups, and draws aggro. Good at the front of a spawn point. |
| Grenade Turret | High damage in a 360° radius, but fragile. Put it behind something. |
| Lightning Turret | Pierces walls, but needs Rubies. The late-game pick. |
Do not build an Armory in the Dusty Caverns — enemies do not appear there at all, so there is nothing to defend.
The rest of the bestiary
Marshy Ruins (bugs): Small Beetles, which are the immature form of Big Beetles and come in hordes; the Flying Bug, which spits projectiles; the Big Beetle, which pinches with its horns; and the Big Mom Beetle, which constantly spawns Small Beetles while it is alive.
Crackling Depths (Vectron drones): the slow melee Zombot, the laser-shooting HoverBot, the Crawling Bot which spawns 2-4 Skull Bots when it dies, and the fragile Skull Bot which flies off to cocoon into a Zombot or HoverBot if you let it.
Creep is not an enemy but it will stop you building: it is a growing mass of vines that slows your bots and blocks construction on those tiles. Only Guards equipped with the flamethrower item destroy it — keep a Guard Quarters with that item.
Abomination (Mechanized DLC) is the toughest and fastest enemy in the game. It roars, summoning 2-4 Skull Bots and panicking every nearby robot including Guards — Mechs are immune. Its shoulder-cannon beam instantly disables machines and destroys blocks as collateral. One Abomination spawns with every Hive attack.
If you have the Mechanized DLC, there is a cheaper answer
The DLC adds two ways to handle a Worm without spending on Thumpers:
- Park a Mech on the Worm’s tile. It cannot attack while the Mech is sitting on it.
- Surround the Worm’s tile with blocks so nothing can path into its reach.
Both work, and both save you the Thumper upkeep.