Sheltering Ancient

A 5/5 trampler for two mana is a body so far ahead of the curve it has to be paid for somewhere, and the upkeep is where the bill comes due: every turn it survives, you hand an opponent's creature a permanent +1/+1 counter, then double down by paying again the next turn, and the next. The arithmetic compounds the way all cumulative upkeep does, but the twist is that the cost isn't life or mana drained from you: it's growth fed directly to the other side of the table. Left unchecked, this is a clock that builds your opponent's blockers while it attacks past them, a race where your own beater fattens the wall it's trying to break through. Most undercosted fatties pay their tax in self-harm or eventual sacrifice; this one funds the opponent's board instead, which turns it into an explicitly short-fuse threat: it wants to end the game before the counters it's donating turn into the thing that stops it. That gives it a clean home in the kind of green aggressive shell that plans to win before the third or fourth upkeep ever arrives, and a clear failure state in any deck that wants to durdle and hold it back. The whole point is to never have to weigh that arithmetic at all, because by the upkeep where it gets ugly, the game should already be over.