Okay, so how much Mana is required to twist reality this extremely, that you can permenantly raise your mental powers, and how difficult is this spell (as in level requirements)?

I'm sorry if I'm being harsh. I'm not trying to rip your ideas apart. I think it's a good one, but just needs some balancing.

One variation I though of is having the spell drain anothers Mana into yourself, increasing your's temporarily (for, say, five seconds) and then you can use that to throw a really big spell back at them. Essentially, you're using their own Mana against them. Or instead of having a timed Mana increase, excess Mana drains away slowly, until it reaches your maximum again?