Zuko, Exiled Prince

Firebending 3 is a combat-only mana burst: the three red pours out when the 4/3 swings and vanishes the instant combat is over, so it can never idle as a mana rock waiting for a better moment. That windfall exists to pay for the ability stapled beneath it, priced at exactly three generic so an attack can bankroll one impulse-draw inside the same combat step: swing, bank the red, then exile the top of your library and cash a card you would never have drawn. But the ability is not chained to the attack. Three of any mana, from lands or rocks, activates it at will, which means the card is not dead if the body stays home; it just runs slower, spending real mana instead of free combat mana to keep the exile engine turning. The impulse clause is what disciplines it: the exiled card is a lease that expires at end of turn, not a permanent gain, so it rewards decks built to empty a hand fast and offers nothing to a player trying to hoard. The synergy is in the sequencing rather than the requirement. Attacking is how the ability becomes free, and the free version is the one an aggressive deck actually wants, but a controlling draw can still feed it off untapped lands and grind through a game without ever committing the body to the red zone.