Collective Nightmare

A -3/-3 that lets your own board pay for itself sets up a strange internal contradiction. The printed cost is three, but that's the ceiling: every creature you tap shaves a generic, and because convoke lets a creature cover mana of its own color, a black creature pays the too. Commit enough bodies and the spell resolves for nothing. The problem is what "free" means here. Convoke was built to underwrite spells that add to the board (tokens, more creatures), where the discount and the payoff push the same direction. Bolting it onto removal inverts that logic: the creatures you tap to make the answer cheap are the same creatures now stuck tapped and unable to block, so the turn you shrink their threat, you hollow out your own defense to do it. Instant speed is what makes the trade worth attempting. Killing a blocker mid-combat or shrinking an attacker after it's declared is a window a sorcery-speed edict never reaches, and spending creatures instead of lands keeps your mana open for whatever else the turn asks. It reads like a Doom Blade with a down-payment plan, but the real axis is board width: whether your creatures can convert their numbers into a one-for-one answer and still leave enough standing to matter afterward. Pay the full three in mana and your board stays untapped to block; lean on convoke and the discount comes straight out of your defensive line.