Miirym, Sentinel Wyrm + Cloudstone Curio + Sneak Attack + Phyrexian Altar

Miirym, Sentinel Wyrm

Cloudstone Curio

Sneak Attack

Phyrexian Altar

How it works

1. Activate Sneak Attack by paying , putting any Dragon from your hand onto the battlefield.
2. The Dragon 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 the Dragon.
5. The token Dragon enters the battlefield, triggering Cloudstone Curio, returning the nontoken Dragon from the battlefield to your hand.
6. Activate Phyrexian Altar by sacrificing the Dragon token, adding .
7. Repeat.