Consumptive Goo

Most repeatable removal that grows the user pays for both halves at once; this one splits the cost into a four-mana-per-activation toll and lets you fire it as many times as you can afford. Each activation shrinks a target by one and feeds itself a permanent +1/+1 counter, so the threat curve and the removal curve are the same line: the more enemy creatures you pick off, the larger it gets, and the size sticks even after the -1/-1 fades at end of turn. That makes it a slow, mana-hungry attrition engine rather than a tempo play. The -1/-1 is also worth noting over plain removal: it shrinks toughness directly, which dodges some of the regeneration and damage-prevention answers that a burn-style effect would run into, and it can finish a creature already wounded in combat. The friction is that the body starts at 1/1 with no protection, so it dies to almost anything before the counters accumulate, and the four-mana activation cost means you are rarely getting more than one or two uses in the turns that matter. It rewards a board where you have mana to spare and time to let the Ooze accrete, which is a narrow ask. The design is honest about its trade: open-ended removal-plus-growth, gated entirely behind how much mana you can sink into it.