Night creature
Now you will know why you fear the night.
Night creatures are a class of hostile creatures. Many of them are generated procedurally, whether as a full creature, through an interaction changing a normal creature, or a mixture of both.
Currently existing night creatures are the following:
Night trolls, which abduct certain civilized creatures of the opposite gender, transform them into a spouse, and mate with them.
Ghosts, the restless spirits of the dead that weren't properly memorialized. Depending on circumstances, they can interact with the living in various ways.
Animated dead are the walking corpses and corpse parts that arise in evil regions or under the thrall of a necromancer or mummy. Particularly evil regions may also transform living creatures into thralls or husks via their unusual weather. They flash between their night creature tile and their basic creature tile.
Necromancers are historical figures that have found the secrets of life and death, becoming immortal and gaining the ability to animate the dead.
Disturbed dead are the dead rulers of civilizations, interred in tombs. They will arise if disturbed and lay curses on the trespasser.
Werebeasts are people cursed by the gods for profaning their temple, or those to whom they transferred that curse. At the full moon, they will transform into a ravenous monster.
Vampires are undead blood drinkers that can pass for living, moving on when suspicion on them grows too much. Occasionally they might start immortality cults instead, and might make a bid to seize power over a whole civilization.