Electro, Assaulting Battery is a rare Legendary Creature — Human Villain card from Marvel's Spider-Man (SPM), collector number 260. Current market price: $4.55 (foil $6.54), TCGplayer market prices via Scryfall.
Flying You don't lose unspent red mana as steps and phases end. Whenever you cast an instant or sorcery spell, add {R}. When Electro leaves the battlefield, you may pay {X}. When you do, he deals X damage to target player.