Demons are one of the most common evil creatures used in games that are based in some kind of hellish setting. Demons are creatures that are dark beings that aim to cause destruction and misery. Befriending demons is not something that is typically seen, even demons seem to hate each other.
Demons are very common in games. While it is normally based on some biblical setting, demons can be used to refer to some kind of horned monster that is an enemy of the player.