Sigil of the New Dawn + Phyrexian Altar + Cathodion + Urza's Incubator

Sigil of the New Dawn

Phyrexian Altar

Cathodion

Urza's Incubator

How it works

1. Activate Phyrexian Altar by sacrificing Cathodion, adding .
2. Cathodion dies, triggering itself and Sigil of New Dawn.
3. Resolve the Cathodion trigger, adding CCC.
4. Resolve the Sigil of New Dawn trigger, causing you to pay 1 to return Cathodion from your graveyard to your hand.
5. Cast Cathodion by paying 1.
6. Repeat.

This cunning loop relies on Cathodion as the engine whose death produces more mana than it costs to recycle. When you sacrifice Cathodion to Phyrexian Altar, its own dying trigger adds three colorless mana, which easily funds the mana requirements of the engine. Meanwhile, Urza's Incubator discounts Cathodion's casting cost by two generic mana, ensuring you can replay the construct for just a single white mana. Finally, Sigil of the New Dawn acts as the recursive glue, letting you pay the exact mana generated to instantly bounce Cathodion right back to your hand for another iteration.