According to familiar Christian mythology, demos are, or were fallen, angels. Satan, for example, was an angel who rebelled against God and was therefore cast out of heaven. Other angels rebelled along with him and became his minions in the underworld. According to mythology, these fallen angels became demons. The mythology assumes that “demon” refers to the same being as “evil spirit.” But there are many angles that were worse than demons, according to various ancient scripts.
Examples of these are the watchers. They appear throughout various books of the bible. In the book of Daniel, the Watchers are holy ones who reside in heaven. Daniel described how a watcher told him that the evil King Nebuchadnezzar of Babylon would eat grass and go insane. In the book of Enoch, an apocalyptic text that isn’t considered a Biblical canon, the watchers are described as fallen angels. Enoch describes how a group of watchers (angels) are tasked with watching over humanity. But many other similar accounts exist, and this video explains the rest.