Imodane, the Pyrohammer 
Legendary Creature — Human Knight
Whenever an instant or sorcery spell you control that targets only a single creature deals damage to that creature, Imodane deals that much damage to each opponent.
Legality
standardLEGALpioneerLEGALmodernLEGALlegacyLEGALvintageLEGALcommanderLEGAL