So, the book states that using Arcana, while most of the time accompanied by hand gestures and other rituals that help the adept, does not really require it and an adept ultimately casts arcana out of sheer force of will.
This begs the question... how can you impair an adepts powers in such a way that may keep them prisoner?
This comes from an adventure I ran for my group, one of the adversaries was a Fire Shaper. They tried to keep bloodshed to a minimum, so the party subdued and tied their adversaries. Problem is, the Fire Shaper could technically still attack them by setting things on fire with his mind. Same goes for his ropes, the building he was in... etc.
We resolved it by all agreeing that keeping tied and muffled was enough to reduce his danger enough till he could be turned over to the proper authorities, but the question kinda lingered.
How do we keep an adept like that (or with other Arcana) a prisoner?