She can beguile my will...
Costed way too high with too low a toughness to be worth anything in competitive Magic outside of limited. I also think she should be a rare instead of a mythic rare. Other than that, I think she's great. I like her ability, but it's just not good enough. Too fragile for an ability that can't be activated for an entire turn. Unless you're telling me she can fit in my Heartless Lich deck because she'll have a chance of coming back repeated, I don't really see it.
We might have to stretch a little to make this one work. So she wants lots of creatures and she wants haste and/or counter magic. That part is clear. Since her ability is conditional upon the power of the creature, maybe spells & abilities that decrease power have a place in this deck. The problem is... there aren't any good spells or abilities that have that function. I'm going to say heavy counter magic featuring four copies of Aether Mutation and Snakeform on this one. That's right, I'm going completely casual. Hopefully your friends will forgive you for playing a counter deck in a casual format because I just don't see this card working any other way.