Zinnia, Valley's Voice + Nesting Dovehawk + Combat Celebrant + The Fire Crystal

Zinnia, Valley's Voice

Nesting Dovehawk

Combat Celebrant

The Fire Crystal

How it works

1. Cast Combat Celebrant by paying 2 plus an additional 2 for its offspring cost.
2. When Combat Celebrant enters, its offspring ability triggers, creating a token copy of it that is 1/1.
3. At the beginning of your combat phase, Nesting Dovehawk triggers, creating a copy of the Combat Celebrant token.
4. Declare a Combat Celebrant token as an attacker, choosing to exert it as it attacks. It then triggers, untapping all other creatures you control and causing you to get an additional combat phase after this one.
5. Repeat from step 3 each combat phase.