Scape and Run: Revenants
Add ominous ghosts to your Minecraft world that pose a deadly threat!
These hostile entities can appear anywhere in your world since they are not bound to specific biomes. However, initially your world is completely free of them.
The Revenants' spawning mechanism is quite interesting: for them to start appearing, regular mobs (not considered undead) must die in combat. After reaching a certain number of non-undead creature deaths in the world, these ghostly beings will begin to materialize.
The ghosts' AI behavior is currently quite basic, but future updates plan to significantly improve their intelligence, add new ghost types with various abilities and unique effects.