When Aang enters, airbend up to one other target creature or spell. (Exile it. While it's exiled, its owner may cast it for rather than its mana cost.)
Whenever Aang and La attack, put a +1/+1 counter on each tapped creature you control.
Aang flashes in at instant speed to tempo-bend a threatening attacker or counter a spell by exiling it, then plays defense while you build toward a Waterbend flip. Once transformed into Aang and La, you swing wide and pump every tapped creature with +1/+1 counters, snowballing your board into a lethal attack. You win through repeatable tempo disruption and a go-wide counter strategy.
Flash + the airbend trigger gives flexible interaction, blanking removal spells or removing blockers/attackers at instant speed
Cheap three-mana body in UW that's easy to recast and protect
The flip side rewards going wide, pumping all tapped attackers each combat
Strong in blink/flicker shells that re-trigger the airbend ETB
Airbend is symmetric-ish removal that only delays threats since opponents can recast for
Waterbend is a steep activation cost that demands real mana investment
The flipped attack trigger only helps if you already have a developed board
UW lacks deep card advantage and ramp compared to other color pairs
Floods the board with tokens that all get counters when Aang and La attack.
Add mana acceleration like Smothering Tithe, Sol Ring, and Mana Vault to consistently afford Waterbend and recast Aang. Lean into a flicker package (Eldrazi Displacer, Restoration Angel, Brago) to abuse the airbend ETB as repeatable interaction, and add token producers plus Intruder Alarm-style untap effects to maximize the flip-side counter payoff.