Ralak, Pawnmaster's Tongue

At any point, you may have target opponent take control of target creature you control. If you do, add {x} to your mana pool, where X was its converted mana cost.
At any point, you may pay {x}. If you do, take control of target creature an opponent controls with converted mana cost X, unless that opponent pays {x}. If you successfully took control of that creature, you lose life equal to its power.