Krovikan Plague

A self-consuming engine dressed up as a pinger. The Aura turns whatever it sits on into a tap-for-one-damage source, but every activation puts a -0/-1 counter on the host, so the creature whittles its own toughness toward zero with each shot. That counter is the balancing tax: the body is borrowing against its own toughness to fire, and the ability can only be activated while the creature is untapped, so a chump-blocked or freshly-tapped host has to wait out a turn before it can pull the trigger again. The delayed cantrip on entry is the era's idea of fairness too, paying you back for the card spent but only at the next upkeep, never the same turn you commit. What it represents is a particular Ice Age-block flavor of slow, attritional black: an enchantment that hands a creature a finite stack of bullets, expects you to aim them, and quietly kills the thing you cast it on if you use all of them. The Wall exclusion in the enchant clause is a tell about intent. This was never meant to weaponize a static blocker into a damage cannon; it wants an active creature you are willing to grind down. A built-in clock on your own permanent in exchange for repeatable reach is a trade the modern game almost never offers, and the counter mechanic now reads as an artifact of its time.