A 3-mana Mardu legend from Avatar: The Last Airbender that adds mana equal to its own power on attack, then counters up your whole team every time a spell or permanent enters from exile.
Impulsive draw and exile-matters decks. Any card that plays from exile — impulsive draw, adventures, foretell — triggers a counters boost on the whole team, turning card selection into a combat trick.
Go-wide aggro. Counters landing on every creature reward a deck that's already committing multiple bodies to the battlefield rather than one big threat.
Combat-trick ramp. The Firebending mana can be spent immediately on a combat trick or activated ability during the same combat it was generated in.
How it does in Commander
As the commander
As the commander it rewards building a full exile-matters shell around it — every impulsive-draw or foretell effect in the deck becomes a repeatable team pump, which is a real payoff for a Mardu go-wide plan.
In the 99
A solid support piece even outside a dedicated shell, since Mardu decks already tend to run some exile-and-cast effects and get a bonus from this without changing their plan.
Formats it's strong in
Exile-matters and impulsive-draw decks. The counters trigger fires off effects the deck already wants to run, making it a natural fit rather than a new build-around cost.
Wide creature boards. A team-wide +1/+1 counter is worth more the more creatures are on the battlefield to receive it.
Formats it's weak in
Decks with few exile effects. Without something casting from exile, the counters trigger simply doesn't fire, leaving the card as a below-rate attacker.
Low-creature-count decks. A team-wide counters trigger is worth much less with only one or two creatures to put them on.
Synergistic cards
Light Up the Stage — A cheap impulsive-draw spell that triggers the counters payoff the moment either exiled card is cast.
Bonecrusher Giant — An adventure card that casts from exile on its second half, triggering the counters ability as a bonus.
Outpost Siege — A repeatable exile-and-cast engine that turns every future draw step into a counters trigger.
Any go-wide token maker — More bodies on the battlefield means more creatures benefiting from each counters trigger.
Is it worth the price?
As a recent-set card, Fire Lord Zuko is affordable and a reasonable pickup for a Mardu exile-matters or go-wide deck — low financial risk to try.