LethalBreed

Build the wall. They will stack blocks under their own feet and step over the top of it.

You know how the night goes. A wall on day three, a roof, a door, and nothing in the game asks anything of you for the next four hundred nights. These zombies place a block, stand on it, place the next, and climb up to 24 blocks that way. The pillar they leave behind crumbles thirty seconds later, which tells you it was never about the wall.

🧱 What your wall actually buys

Nothing here walks through stone. Everything eats it. A zombie standing against a block adds 0.04 points of progress per tick, divided by that block's hardness, and the block drops at 1.0. Stone holds for 1.9 seconds.

Past a hardness of 30 they refuse the block outright. Obsidian holds, and now you have something to do with your evenings.

They do not queue up, either. One about to start digging looks for a neighbour already working nearby on something that would serve it too, and joins that one instead. The breach opens where the crowd is.

🪜 Over, under, around

• Digging under, bridging a gap and swimming are all open to them. A moat is a detour, and in deep water they climb on each other to get out.
• The break height comes from the body, one to four blocks, so a bigger specimen opens a bigger hole.
• Break line of sight and they head for the last place they had you. A noise anywhere near writes them a new one.
• Chests, furnaces, beds and spawners are left standing. They take your wall apart, not your storage.

🌞 The sun stops saving you at tier 5

A phase counter starts with the world and climbs on the world's own age, one tier every thirty minutes of it, give or take three. It ignores the day cycle, it survives restarts, and it never falls back. /lethalphase says where you are.

Tier 5 is where daylight stops burning them. From there the morning is a change in the light and nothing else.

They carry no gear at any tier. The escalation is all statistics and potion effects, bending onto a ceiling they approach without reaching, which is why tier 30, tier 50 and tier 100 still feel different from one another.

🧟 Eight of them are not normal

The odds of a specimen drawing a variant climb with the phase, up to 35% of them. No name floats overhead, so you find out by what it does.

• Sprinter, permanently quicker than the rest
• Leaper, clearing ground a body that size should not
• Screamer, pulling every idle zombie within 24 blocks onto you
• Healer, putting the wounded ones back on their feet
• Juggernaut, twice the health, and bigger wherever the ceiling lets it stand
• Necromancer, calling in more
• Splitter, becoming two when it dies
• Bomber, which never has to touch you

The Bomber stops three blocks short, freezes, and swells for anywhere from one and a half to six seconds. That pause is your window and it is the whole of it. A longer fuse means a stronger blast and filth thrown further. It breaks nothing: the walls come through it, you are the only target it has. Its ring of filth carries half again as far as the blast, so stepping clear of the lethal radius saves hit points and infects you anyway.

🦠 The plague you cannot see

Super Contamination gives you nothing to read while it is latent. No icon, no damage, no sign. The one clue is half a second of slowdown at the moment it takes.

Then it waits. Every five to ten in-game days it rolls once, with a small chance of turning, so a carrier usually goes hundreds of days before the first symptom, and then it arrives in five worsening stages.

Three of its four routes need no blow at all: a Bomber's filth, the pool that filth leaves behind, and a potion brewed from rotten flesh. Armour has no bearing on any of them. Milk takes the icon away and hands it straight back.

A villager who dies carrying it gets up again on the other side.

🔧 Built for the crowd

The pathfinding is a distance field recomputed every ten ticks on its own pool, off the server thread, over a grid bounded to 192 blocks. The tick scheduler is built around a thousand active zombies at once.

Where an OpenCL device exists the field goes to it, and JOCL travels inside the jar, so nothing gets installed on the host. No device, or a device that errors, and it drops to a multi-core solver that returns the same paths. A headless server without a graphics card plays the same game, on more cores.

The simulation runs server side and nothing is pushed to a client on join. The client half is optional and carries the contamination overlay, the hallucinations and the settings screen. /lethalconfig opens those, operators only.

🛑 Before you install

Any mod that alters zombie AI will stop this one from launching. It drives that AI itself, so the two cannot share it. Caught at startup, the game does not launch. Caught mid-session, the server stops cleanly and your world is saved. Everything that leaves zombie AI alone is fine, performance mods included.

Modpacks are welcome, and so are forks and addons, with nothing to ask for first. A mention is welcome too, never required.

Every mechanic, every value and every command, in French and English, with a breach calculator that runs the server's own arithmetic: