Colfenor, the Last Yew + Myr Retriever + Ashnod's Altar + Su-Chi

Colfenor, the Last Yew

Myr Retriever

Ashnod's Altar

Su-Chi

How it works

1. Activate Ashnod's Altar, sacrificing Su-Chi to add CC.
2. Su-Chi and Colfenor trigger.
3. Resolve the Su-Chi trigger, adding CCCC.
4. Resolve the Colfenor trigger, returning Myr Retriever from your graveyard to your hand.
5. Cast Myr Retriever.
6. Activate Ashnod's Altar, sacrificing Myr Retriever to add CC.
7. Myr Retriever triggers, returning Su-Chi from your graveyard to your hand.
8. Cast Su-Chi.
9. Repeat.