Sprouting Phytohydra

The damage trigger inverts the most basic instinct in combat math: hitting it is how you make more of it. A defending 0/2 that copies itself whenever it takes damage punishes any answer that touches it without a plan, because the trigger fires on damage of any kind, lethal included. Burn the original for two and it dies, but the death does not cancel the reward; the trigger still resolves off last known information and hands you a fresh copy anyway, so the net result is a wall for a removal spell. The trade gets worse for the attacker the smaller the damage. A 1-power creature that swings in does not kill the 0/2, so the original survives and the trigger spawns a second wall: now there are two where there was one. A pinger tapping for a single point a turn does not slowly grind it down; it builds you a thicket. The defender clause keeps the design honest about its lane: this thing never attacks, so multiplying it deepens a stalled board rather than assembling a clock. It lives entirely on the attrition axis, taxing removal and ground assaults by making the act of interacting with it the thing that funds your defense. The trap is that it reads as a speed bump and behaves as a counterpunch, and the counterpunch lands hardest on the player who reaches for a small, repeatable damage source instead of a clean one-shot kill.