A Demon is a creature from the outside. An entity from whatever horrible realm the Dark Watchers dwell in when they are not terrifying Vosca. Demons are malformed, hideous creatures that are maladjusted to life on Mundus. They suffer constantly, and their anguished throes are the source of much destruction.
Demons have no consistent shape or size. Each seems to be unique, though some are similar to each other in ways that suggest kinship. They vary in intelligence from animal to superhuman, but none have yet been found that can communicate meaningfully with men.