Silence

"This magic doesn't just silence outside sound but inner voice as well, so those under the effects of Silencing are first disoriented as their entire universe becomes quiet. Spell-casters find themselves deprived of supernatural command."

This spell causes the target to become silenced and can be used to counter magic, making it potentially OP, using their mental capabilities, their will, and their knowledge of the arcane world to cast.

However, the target can attempt to resist this spell using their awareness of their body, their dexterity, and their own raw will and knowledge of the arcane to resist: essentially, a bunch of different traits. This makes Misfortune a much better spell to counter pesky magicians, although it can't shut them up for a whole battle, whereas Silence can keep that annoying mage out of the picture for an entire Scene.