They Are Legion
by Markus-Otto
Persistent zombie hordes that migrate, grow over time and react to player activity are added to the world by They Are Legion.
What it does
Instead of spawning huge numbers of entities, the mod simulates each horde as a lightweight server-side population with a position, behavior, target, movement state and saved data per dimension. A horde only materializes into real vanilla zombies when it gets close enough to matter to nearby players, so the server keeps a large horde without ticking thousands of entities. Hordes are also kept loaded at the real entity level once they become relevant.
Player activity leaves signals in the world. Mining, fighting zombies, building and general base presence add to a heat and noise system that attracts alerts from nearby hordes, and the populations grow as Minecraft days pass. Evolution modes can be configured. The mod is intended to pair well with the Turret TaCZ Addon, a companion whose automated turrets and firearms give a large threat a purpose.
Installation needs Forge, and the mod runs on client and server, so the server and every player need it. Files are published for Forge only, for six game versions 1.20.1 – 1.20.6, with 0.5.1-beta for 1.20.6 as the latest file in the beta channel. The MIT License covers the mod, which is not open source.
Key features
Persistent zombie hordes
Hordes stay in the world, are saved per dimension and keep their state between play sessions.
Horde migration
Hordes move through the world over time rather than appearing only as instant events.
Heat and noise alerts
A heat and noise system draws hordes toward players whose activity generates enough signal.
Natural horde spawning
Hordes spawn around players naturally, creating a living undead threat across the map.
Configurable evolution
Evolution modes can be set to control how hordes grow and change over the course of a world.
Gallery
Compatibility
Latest build for each game version and loader.
Only full game releases are shown. This mod publishes no snapshot builds.
Use cases
Survival defense
Players who build a fortified base can face roaming hordes that apply siege pressure over time.
Modpacks with combat mods
The mod is meant to work alongside infection, zombie combat, weapon and survival overhaul mods.
Who it’s for: Players who want a persistent zombie threat that reacts to their base and their activity, and server owners who need large hordes without the cost of thousands of ticking entities.
Questions
Does They Are Legion need to be installed on the server?
Which Minecraft versions does They Are Legion support?
Does the Turret TaCZ Addon have to be installed?
More from Markus-Otto
What the author says
They Are Legion adds persistent zombie hordes to Minecraft. Instead of spawning huge numbers of entities all the time, the mod simulates hordes as lightweight server-side populations, then materializes real vanilla zombies only when they become relevant near players. The goal is to create the feeling of a living…
Official listing
- Modrinth page
- modrinth.com/mod/they-are-legion
- Owner
- Markus-Otto
- Published
- 2026-06-23
- Updated on Modrinth
- 2026-07-08
- Facts verified
- 2026-10-15