Appa, Steadfast Guardian + Umori, the Collector + Restoration Angel + Cloud Key

Appa, Steadfast Guardian

Umori, the Collector

Restoration Angel

Cloud Key

How it works

1. Cast Appa by paying
2. When Appa enters, its first ability triggers, exiling Restoration Angel with the ability to cast it later from exile.
3. Cast Restoration Angel from exile by paying 0.
4. Appa's second ability triggers, creating a 1/1 Ally creature token
5. When Restoration Angel enters, it triggers, blinking Appa.
6. Repeat from step 2.