Demons are beings whose appearance and ability vary between one and another, but what they all share in common are the ability to use powerful magic (including forbidden Time Magic) and inherent dark nature compared to regular magical creatures. They also have a significant influence on human culture, as it was known that demons tempted many mortals to make a pact with them in exchange of their wishes (be it power, status, etc.) granted and their body parts (ex. horn) can be used as ingredients for enchantments. However, due to the demons' own treacherous nature and harm from establishing a pact with them (wishes granted from the said pact always come with a price which including one's life), witches eventually became wary towards them and deemed them untrustworhy. Although, this doesn't deter some witches from willingly made a pact with these creatures out of either selfish or malicious reasons.
While yet to be confirmed, the demons' aforementioned role was one of catalysts of Witch Hunts.