Doc Aurlock, Grizzled Genius + Aang, the Last Airbender + Appa, Loyal Sky Bison

Doc Aurlock, Grizzled Genius

Aang, the Last Airbender

Appa, Loyal Sky Bison

How it works

1. Cast Aang by paying its mana cost.
2. When Aang enters, it triggers, airbending Appa.
3. Cast Appa from exile by paying 0 due to Doc Aurlock.
4. When Appa enters, it triggers, airbending Aang.
5. Cast Aang from exile by paying 0 due to Doc Aurlock.
6. Repeat from step 2.