Something out there is pretending to be one of you.

A Fabric mod for Minecraft 1.21.1 that adds the Skinwalker, a creature that steals the name and skin of a real player and walks around like one, until you get too close.

• It looks like one of you. When a Skinwalker spawns, it copies a random online player: their skin, their name and their name tag. Alone in singleplayer, it is Steve or Alex instead.
• It acts like a player. While disguised it wanders around, punches out logs, dirt and sand, and places the blocks it carries.
• Don't get close. If a player comes within a few blocks, it reveals its true form.
• It hunts. In monster form it is fast, strong and over four blocks tall, hunching down to squeeze under trees and low ceilings. If it loses its prey, it shrinks back into the same stolen disguise, and after a short rest it slowly heals.
• Where: on the surface of every overworld biome (except mushroom fields), day or night. By default it is four times rarer than an Enderman.
• Drops: 1–2 Distorted Totem Shards (more with Looting) and, if killed by a player, the head of the player it was imitating.

Health carries over between forms as a percentage, so a hurt disguise turns into a hurt monster.

Crafted from 4 Distorted Totem Shards around a bone. Hold it like a Totem of Undying: when you would die, it saves you with 1 HP, but you are Marked by Death and blinded by Darkness for 30 seconds.

Marked by Death: every mob within a configured amount of blocks hunts you, including animals, villagers and other players' pets. Your own pets spare you.

Crafted from 2 bones, a ghast tear, an amethyst shard and 3 gold blocks (bones and tear on top, amethyst in the middle, gold blocks at the bottom). Mine it with a pickaxe.

• Right-click with any item to place it on the altar; right-click with an empty hand to take it back.
• Place a Distorted Totem on the altar, then right-click it with a Golden Apple to purify it into a Totem of Undying.
• Hoppers can insert into an empty altar and take items out of it.

The mod has its own Skinwalker tab in the Advancements screen:

Every setting can be changed in-game from the Mod Menu Mods list (select Skinwalker, then the settings button), or in config/skinwalker.json5. Changes made on the settings screen apply immediately; after editing the file by hand, restart the game or server.

The settings belong to the server. In singleplayer the settings screen controls them directly; on a dedicated server, edit config/skinwalker.json5 on the server. Settings changed on a client do nothing on someone else's server.

Requires Fabric Loader 0.16.14+ and Java 21. Additional mods required:

• Fabric API
• Cloth Config (15.0.140+)
• Mod Menu (optional, needed for the in-game settings)

On a server, install the mod, Fabric API and Cloth Config on both the server and every client.