TC3 League. Regular Season.

How interesting is that? :D
If the most expensive spell in the book has a usefulness of 10 (blindness).

3*10=30 mana, 80.

I said that in principle it's possible, i.e., casting Berserk (non-expert) against an opponent with Pegasi. After 3 rounds, you'll have almost 0 mana ;)