Sigil of the New Dawn + Pawn of Ulamog + Phyrexian Altar + Ornithopter

Sigil of the New Dawn

Pawn of Ulamog

Phyrexian Altar

Ornithopter

How it works

1. Activate Phyrexian Altar by sacrificing Ornithopter, adding .
2. Pawn of Ulamog and Sigil of the New Dawn trigger.
3. Resolve the Pawn of Ulamog trigger, creating a 0/1 Eldrazi Spawn creature token.
4. Activate the Eldrazi Spawn by sacrificing it, adding C.
5. Resolve the Sigil of the New Dawn trigger, causing you to pay 1 to return Ornithopter from your graveyard to your hand.
6. Cast Ornithopter by paying 0.
7. Repeat.