Miirym, Sentinel Wyrm + Cloudstone Curio + Mothdust Changeling + Phyrexian Altar

Miirym, Sentinel Wyrm

Cloudstone Curio

Mothdust Changeling

Phyrexian Altar

How it works

1. Cast Mothdust Changeling by paying .
2. Mothdust Changeling enters the battlefield, triggering Cloudstone Curio and Miirym.
3. Resolve the Cloudstone Curio trigger, choosing not to return anything to your hand from the battlefield.
4. Resolve the Miirym trigger, creating a token copy of Mothdust Changeling.
5. The Mothdust Changeling token enters the battlefield, triggering Cloudstone Curio, returning the nontoken Mothdust Changeling from the battlefield to your hand.
6. Activate Phyrexian Altar by sacrificing the Mothdust Changeling token, adding .
7. Repeat.