Greven, Predator Captain

Most attacking payoffs ask you to build up a board; this one asks you to spend life and creatures faster than you can replace them, then rewards the recklessness. The +X/+0 clause reads life loss as a resource, so self-damage engines (Bolas's Citadel effects, painlands, phyrexian mana, life-loss tutors) stop being a tax and start being fuel: every point you bleed swings a red-hot 5/5 with menace that much harder. The attack trigger is the real engine, though, and it inverts the usual sacrifice-value math. Where most sac outlets convert a creature into a fixed payoff, this one splits the creature's stat line into two separate ledgers: power becomes cards drawn, toughness becomes life lost. That coupling is the whole design idea. Feed it a big-power, low-toughness creature and you refill your hand for almost nothing; feed it a fat wall and you gut yourself for a card or two. It turns deckbuilding into a hunt for lopsided bodies (Ball Lightning types, hasty attackers you were going to lose anyway) and quietly discourages sacrificing the durable blockers you actually want to keep. And because the life you pay for those cards immediately feeds the buff, the two abilities loop into each other: the sacrifice that draws you three fills the attacker that closes the game. It is a rare piece of design where drawing cards and hitting harder are the same gesture, paid for in the same currency.