When Appa enters, its first ability triggers, exiling Wispweaver Angel with the ability to cast it later from exile.
Cast Wispweaver Angel from exile by paying 0.
Appa's second ability triggers, creating a 1/1 Ally creature token.
When Wispweaver Angel enters, it triggers, blinking Appa.
Repeat from step 2.
This clever loop relies on Hamza, Guardian of Arashin to discount creature spells based on your +1/+1 counters, effectively making Wispweaver Angel free to cast from exile. When Wispweaver Angel enters the battlefield, its blink ability targets Appa, Steadfast Guardian, sending the Guardian into temporary exile. Appa then re-enters the fray and immediately triggers to airbend Wispweaver Angel right back into exile, while its second ability rewards your exiled-spellcasting with a steady stream of 1/1 white Ally creature tokens.