Pestilence Demon

Pestilence-on-a-stick, with all the gambling the stapling implies. The repeatable ping is the engine black sweepers have run on for decades: pay one black, hit everything, repeat until the board is empty or your life total is. The wrinkle is that here the engine arrives attached to its own clock, a 7/6 flier that takes the symmetrical damage it dishes out right along with everything else. That changes the math entirely. A standalone repeatable wrath punishes you for having no board; this one is the board, so every activation that clears the opposition leaves you with a flier in the air and a life total you can spend down toward one. The cost is the rest of the package: eight mana is steep, the body has only six toughness so the sixth straight activation kills the demon along with whatever it was trying to clear, and each activation hits you alongside everyone else, so the damage burns from two directions at once. What complicates it is that it wants to be the last thing standing in a stalled, grindy game, and it pays its full eight up front just to hit the table, then feeds it a black at a time to both clear the path and survive the clearing. It is the rare creature that is also its own removal spell and its own win condition, both folded into one mana value that asks you to wait for the turn it can do all of it.