They ruled the galaxy a billion years ago before being imprisoned by the Timeless Ones. They have tried on multiple occasions to escape their prison, often with the aid Felix Faust who frequently summons them. On of the demons, Abnegazar, was slain by Dr. Fate though he was soon brought back to life by his brothers, albeit as a large, demonic maggot. They later joined with Neron in his plot to kill the Justice League. While not as powerful as himself, Neron apparently respected the elder demons. They also aided the Society led by Alexander Luthor by kidnapping Nightshade during the Day of Vengeance.
The Demons Three attack Constantine, Black Orchid, Dr. Mist, Deadman, and Zatanna in The House of Mystery. They escape with the map to The Books of Magic, escape the limbo realm, and jump into a portal that takes them to where Felix Faust is being held by Steve Trevor. They tell them they are there for The Black Room.