A game I'm working on uses 魔力 too. I just translated it as "mana" though since it's a substance which can be spent/drained (in my case) and they mention it a lot so mana ends up reading better. Though I probably would've stuck with "magical power" if it was the kind of thing which was mentioned once, in the tutorial.
Anyway, I'm ready for us to be done with this gunner guy.