Colfenor, the Last Yew + Myr Retriever + Ashnod's Altar + Cathodion

Colfenor, the Last Yew

Myr Retriever

Ashnod's Altar

Cathodion

How it works

1. Activate Ashnod's Altar, sacrificing Cathodion to add CC.
2. Cathodion and Colfenor trigger.
3. Resolve the Cathodion trigger, adding CCC.
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 Cathodion from your graveyard to your hand.
8. Cast Cathodion.
9. Repeat.