Toph, the First Metalbender + Ugin's Nexus + Meticulous Excavation + Extruder

Toph, the First Metalbender

Ugin's Nexus

Meticulous Excavation

Extruder

How it works

1. Cast Ugin's Nexus by paying 5.
2. At the beginning of your end step, Toph triggers, causing Ugin's Nexus to become an artifact land creature.
3. Activate Extruder by sacrificing Ugin's Nexus. Ugin's Nexus is exiled instead of being put into your graveyard, causing you to take an extra turn after this one.
4. Toph triggers, returning Ugin's Nexus from exile to the battlefield.
5. Resolve the Extruder ability.
6. Activate Meticulous Excavation by paying 2, returning Ugin's Nexus from the battlefield to your hand.
7. Repeat each turn.

This clever engine achieves infinite turns by continuously looping Ugin's Nexus through the battlefield and exile. Because Toph, the First Metalbender turns your nontoken artifacts into lands, Extruder can sacrifice Ugin's Nexus to its own ability, triggering the Nexus's replacement effect to exile itself, grant you an extra turn, and allow Toph's delayed trigger to return it to the battlefield. Finally, Meticulous Excavation provides an alternative way to reset the loop by bouncing the artifact straight back to your hand if needed, keeping the extra-turn cycle rolling indefinitely.