Prototype Portal + Clock of Omens + Grinding Station + Great Furnace

Prototype Portal

Clock of Omens

Grinding Station

Great Furnace

How it works

1. Activate Prototype Portal by paying 0 and tapping it, creating a token copy of Great Furnace.
2. The Great Furnace token enters, triggering Grinding Station, untapping Grinding Station.
3. Activate Clock of Omens by tapping the Great Furnace token and Grinding Station, untapping Prototype Portal.
4. Repeat.

By feeding a zero-cost artifact land—imprinted onto Prototype Portal—into the loop, you gain the engine's entire fuel source right from the token's creation. As the Great Furnace token enters the battlefield, Grinding Station’s triggered ability immediately untaps itself to stay ready for the next iteration, while Clock of Omens uses that very same token alongside the milling artifact to untap Prototype Portal. This tight loop endlessly generates tapped artifact lands and mills your opponents out through Grinding Station's relentless triggers.