Atraxa, Unifier of All

Flying, indestructible, hexproof, vigilance, deathtouch, lifelink, toxic X

X is the total power of creatures you control.

Whenever an opponent casts a spell, you gain control of target creature that player controls with converted mana cost less than X

{t}{w}{u}{b}{r}{g} You gain X life and each opponent sacrifices X creatures. If they can't, they get X poison counters