Electro, Assaulting Battery (Marvel's Spider-Man #260)

Legendary Creature — Human Villain - {1}{R}{R}
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.
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