Zk'rkrzyx, the Eternal Rage

Trample, Haste
Whenever Zk'rkrzyx, the Eternal Rage attacks, it
gains +X/+0, where X is the total amount of
damage dealt to you by sources defending player
controls since your last turn.
Whenever Zk'rkrzyx, the Eternal Rage becomes
the target of a spell or ability an opponent
controls, it deals 4 damage to that player.