The Midnight Lurker

This mod adds a new mob to the game that has a chance to spawn at night or in caves and it's main goal is to scare the player.

The Midnight Lurker Mod (1.20.1, 1.19.4) is a horror mod that adds a new terrifying mob to the game. This creature spawns at night or in caves, attempting to scare the player. It appears near the player, waiting for them to discover it. If you look at the mob, you can frighten it away. However, if you approach the creature without looking, it will immediately attack you. And don’t even try to hide from it behind wooden doors, as it will easily break them to reach you.