The Midnight Lurker

The Lurker appears at night or in caves and waits for the player to find it. Looking directly at it makes it teleport away. Approaching without looking at it aggravates it, and it chases the player for about a minute; if it cannot catch them, it teleports off. An aggravated Lurker also breaks wooden doors used to lock it outside, unless the build uses iron doors.

Several variants extend the mob in later builds. The Faker jumpscares the player and raises their insanity stage by one. The Hider sinks into the ground when looked at and leaves a Void Gateway behind if approached too closely. Stalkers in dark places, Shapeshifters in villages that can lure players into trading, and a Neutral/Runaway that watches the player before fleeing or approaching are also included. The mod is open source under the MIT License and runs on client and server, so both the server and every player need it. Files cover 1.18.2, 1.19.2, 1.19.4 and 1.20.1, with 4.0.0-D2-beta for 1.20.1 as the latest beta file.