[quote=NarcissisticPotato]
Edit:Avalon is both, kind of. Any Metas that are deemed weak are held in the high-security section that most of the Magi oversee. Deeper into Avalon, the A-Class and B-Class metas are stored in the sleeper facility that is controlled by the Magi Hypnos, a SS-class Meta who can put someone into a coma and keep them in that state. Avalon is usually the spot where rogue S-class and SS-class Metas are put down.
[/quote]

Stephen never told me anything about the origins of the power, but due to the fact that I've been making the lore up as I go along, I'm sure I can find a reason for that!