Demon: The Fallen is a role-playing game and a fictional setting from the World of Darkness line by White Wolf Game Studio. The player characters in the game are fallen angels, who were cast out of paradise after a thousand year war with "God". This war was started by Lucifer, after he defied God's wishes for humanity. After losing, the rebels have been cast into Hell as a punishment. While in Hell, these angels were transformed into Demons. Some seek revenge upon humanity for being the primary cause for the war, while other Demons want to reconcile and repent for their sins, to be able to return to God.

For some unknown reason, the Gates of Hell that kept the Demons from breaking free from their prison have begun to weaken, allowing Demons to escape. However, to continue existing, a Demon must find a suitable host for itself: bodies with weak souls, for example comatose patients, severe drug addicts or suicidal people. The Demon severs the weakened soul from the body and takes its place inside the host, merging with the host's memories and emotions, and continues existence on Earth to follow its own personal agenda, sometimes hindered by the memories and feelings the mortal soul left behind.

All characters must choose a "house" and a "faction". The seven houses are similar to races in other RPGs, and to clans in Vampire: The Masquerade and similar groupings in other White Wolf games. The different factions are based on the demons' personal opinions and positions regarding the war. All demons can use special magical powers called Lores. All demons have an "apocalyptic form". This is a mirror image of their true nature, their form before they were forced into mortal bodies. They can be demonic, and horrible to behold, or angelic and beautiful, depending on the Demon.

Houses

• Defiler (or Lammasu)
• Devil (or Namaru)
• Devourer (or Rabisu)
• Fiend (or Neberu)
• Malefactor (or Annunaki)
• Scourge (or Asharu)
• Slayer (or Halaku)

Factions

• Faustian
• Cryptic
• Luciferan
• Ravener
• Reconciler