Dark Cultists are Animals. This monster type is likely called a "Cultist," and "Dark" is a prefix denoting their particular type, but this is not yet confirmed.

Cultists are human mages who spawn with Berserkers. Cultists are very weak, but they can shoot fireball projectiles and summon powerful Dark Demons, so it's wise to bypass the hulking Berserkers to kill the Cultists as quickly as possible.

Cultists can be recognized from Vessels by their lack of a staff. Vessels have a long staff which curls at the end, on which they lean while summoning up the demons by which they are possessed.

Media

Cultist concept art and screenshots in the Image Gallery.