Dogpile

The damage scales with your committed attackers, which means this is a reward, not a removal spell: it only pays out for a board already invested in combat. Cast it on an empty turn and it does nothing; cast it during a wide swing and it doubles as a finisher that can clear a blocker, burn the opponent's face, or punish a defensive wall after they've decided how to allocate blocks. Four mana is steep for an instant whose floor is zero, and it asks the deck to be the go-wide aggressive shell that generates the bodies in the first place. The instant timing is where the math gets dangerous: you wait for blocks to be declared, watch the opponent commit defenders, then point the burn at a creature they thought was safe or at the player they thought was protected, all while your count of attackers is at its peak. This is one of red's attack-step payoffs, the effects that bill the swarm twice: once in combat damage, once in burn. The reward is real only when the board is real, and that conditional payout is what keeps a spell this open-ended from being a windmill-slam in every deck.