Crumbling Ashes

The trick here is conversion of state. A -1/-1 counter is ordinarily a finished transaction: it shrinks a creature once and never again, a permanent stat reduction that the board moves past. This enchantment reads that counter not as a debuff but as a mark, and the mark never expires. Size becomes irrelevant once a counter lands: a 12/12 with a single -1/-1 counter is queued for execution exactly as surely as a 3/3, because the trigger checks for the counter, not the resulting toughness. Truly indestructible creatures still walk away (this destroys, and the counter does not change that), but anything that can be destroyed and carries a counter is living on a clock. The upkeep timing is what pays for that open-ended targeting. There is a full turn of lag between marking a creature and killing it, the opponent gets a window to respond or sacrifice the doomed creature, and the trigger fires exactly once per cycle no matter how many counter-bearing creatures sit across the table, so a wide board outpaces it. None of this happens without a source of -1/-1 counters, which makes the enchantment one half of a two-card engine rather than removal that stands alone. Feed it a steady counter supply and it grinds: each upkeep one marked creature dies unless it can race or answer the enchantment. It is attrition machinery for a deck built on the counters axis, not a clean immediate kill.