Bladewing's Thrall + Cloudstone Curio + Mothdust Changeling + Phyrexian Altar

Bladewing's Thrall

Cloudstone Curio

Mothdust Changeling

Phyrexian Altar

How it works

1. Cast Mothdust Changeling by paying .
2. When Mothdust Changeling enters the battlefield, Cloudstone Curio and Bladewing's Thrall trigger.
3. Resolve the Cloudstone Curio trigger, choosing to return nothing to your hand.
4. Resolve the Bladewing's Thrall trigger, returning it from your graveyard to the battlefield.
5. When Bladewing's Thrall enters the battlefield, Cloudstone Curio triggers, returning Mothdust Changeling from the battlefield to your hand.
6. Activate Phyrexian Altar by sacrificing Bladewing's Thrall, adding .
7. Repeat.