Arcbond

A retaliation clause compressed into a single instant: choose a creature, then arm a delayed trigger that fires whenever that creature takes damage this turn. The chosen creature still eats the original hit; what the trigger adds is a fresh burst of damage the creature then deals to each other creature and each player, sized to whatever landed on it. So the evaluation inverts what most red instants ask. Instead of finding a body worth burning, you find damage worth amplifying, and the cleanest way to guarantee an event is to supply it yourself: point Arcbond at a creature you are about to burn, aim the burn at the same creature, and the follow-up scales with the size of your source rather than the toughness of the target. Hit a creature already committed to lethal combat and the splash lands as a second blow across the board.

The vulnerability is written into the same clause that powers it. The trigger keys on a damage event and nothing else, so a destroy or exile effect in response removes the chosen creature before any damage arrives, and the spell does nothing. That is the tax on building around a delayed trigger rather than a stand-alone effect. Resolve it on your terms, though, and the same cast that sweeps the board can close a game from across the table, because the new damage hits every player right alongside every creature.