Plague Sliver

A hoser stapled to a member of the tribe it hoses. The damage clause grafts itself onto every Sliver on the battlefield, but it points at the controller's own life total, not the opponent's, so the more committed you are to the tribe, the harder the rider bites. The 5/5 body is generous on purpose: the rate that looks like a steal is paid for in upkeep damage that scales with your own swarm. Cast alone against a dedicated Sliver board, it is pure disruption, quietly converting an opponent's army into a self-inflicted clock while your single creature does the hitting. Add it to your own pile and it becomes a Faustian threat: a fat early body that accelerates your own bleed as the board fills out. The text reads symmetrical, but the symmetry is a feint. Both players take damage per Sliver they control, and the player who has invested most in Slivers is almost always the one who reached for the tribe to begin with. That is the elegance: the worse the deck is for the opponent to face, the worse it is for them to have built. There is no clean exit, because the cost is indexed to the very commitment that makes a Sliver deck a deck at all.