| The subject of this article is non-canonical.|
While created as part of licensed material, it has not been confirmed as part of the "real" Buffyverse.
"The Belial Siphon is the stuff of legend. The most powerful of all spells, never to be used lightly. Never to be used at all, in fact."
The Belial Siphon was one of the most dangerous and terrifying spells known to mankind. It was so feared that Spike had regarded it as a myth, Anya stated no self-respecting demon would even think of trying it, and the Watcher's Council had placed a strict ban against its usage.
The Belial Siphon was an undoing spell that could reverse all magic, actions, thoughts, and even time itself. However, it was supremely dangerous in the sense that it could not be controlled. One could cast the spell, but it would undo whatever it wanted, and not even the caster could dictate the terms. The Siphon would undo however much it decided to undo, and hence could undo the fabric of reality itself, effectively destroying the universe.
Neither Giles nor Willow had read anything about it actually being used, though Willow had heard bits and pieces of information about the Siphon when she first started studying witchcraft. It gave her the impression that the Siphon was like the Boogeyman of spells: something all other Wiccans whispered about and feared despite the complete lack of hard facts about it.
When the Scooby Gang found themselves dealing with what seemed to be the one true natural apocalypse, Willow suggested the Belial Siphon, unwilling to give up without a fight,
- Apocalypse Memories (non-canon)