Appa, Steadfast Guardian + Urza's Incubator + Aang, Airbending Master

Appa, Steadfast Guardian

Urza's Incubator

Aang, Airbending Master

How it works

1. Cast Appa either from your hand or from the command zone by paying plus commander tax if applicable.
2. When Appa enters, it triggers, airbending Aang.
3. Cast Aang from exile by paying 0.
4. Appa triggers, creating a 1/1 Ally creature token.
5. When Aang enters, it triggers, airbending Appa.
6. Cast Appa from exile by paying 0.
7. Repeat from step 2.