Spontaneous Combustion

A Pyroclasm with a tollgate built into the casting cost. The interesting tension is the additional cost: sacrificing a creature is not a sweetener attached to a board wipe, it is the gating mechanism that decides who actually wants the effect. A control deck that would happily three-damage every creature has nothing to feed it; a sacrifice-leaning Rakdos deck has fodder to spare and turns the cost into upside, converting a token or a dying attacker into a symmetrical sweep. That is the design idea worth noting: by routing the spell through a sacrifice, the card self-selects for the exact archetype where the symmetry stops being symmetric. The instant timing is the other half. Most board wipes in this damage range arrive at sorcery speed, so they telegraph; this one can wait for a combat step, eat a creature mid-attack, and reset the board after blocks are declared. Three damage to each creature is a modest ceiling by later standards, but the friction here was never the rate. It was that you had to want to give something up to fire it, and the cards that wanted to do exactly that have always been the ones that made it sing.