Bloodsoaked Champion

The recursion clause is the whole machine here, and the two restrictions wired into it are what keep a one-mana repeatable body from being free. Raid gates the return behind a swing you've already made, so the card only crawls back if you were pushing the board forward anyway rather than handing you a chump blocker in a stalled game; the can't-block clause makes sure it never plays defense even once. What you're buying is a creature that refuses to die in any way that matters: sacrifice it to an outlet, trade it in combat, feed it to a removal spell, and as long as you keep attacking it returns for two mana, turn after turn. The result behaves less like a body than a renewable resource. Sacrifice decks that loop death triggers care about that property far more than they care about the 2/1: a creature that returns on demand is fuel that never runs dry, and the attack requirement is a small tax for a deck already racing. It sits in a narrow lineage of recursive one-drops that ask you to pay a little each time instead of staying dead, the structural cousin of Gravecrawler's tribal loop and Reassembling Skeleton's pay-to-return, but tuned for the attacker rather than the blocker. The price of admission is that it can only ever push damage, which is exactly what the deck that wants it is already doing.