Deathgazer

The deterrent is the whole design: a body that punishes any nonblack creature for entering combat with it, on either side of the attack. The text reads like a deathtouch effect with a color clause bolted on, but the structural difference matters. Deathtouch resolves through combat damage, so a first-striker that kills the blocker before it deals damage never takes the deathtouch hit at all; this triggers at end of combat no matter how the damage shakes out, which means a creature that survives the exchange still dies, provided it is not black. That color exemption is the balancing friction. Against a mono-black board the lizard is a vanilla 2/2 with no edge at all, and the mechanic rewards the kind of color-pie politics this era leaned into, where black's contract with its own kind was a recurring theme. The trigger has its limits, though: it fires only in combat and only once a block is committed, so it deters trades rather than forcing them. An opponent simply declines to block and accepts two damage, or holds a black creature in reserve to wall it for free. An indestructible nonblack creature is the cleanest answer, since "destroy" can do nothing to it; the lizard's bite is real but conditional, a wall that punishes only the boards that have committed to colors which cannot safely meet it in combat.