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

Toph, the First Metalbender

Ugin's Nexus

Meticulous Excavation

Coastal Hornclaw

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 Coastal Hornclaw 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 Coastal Hornclaw ability.
6. Activate Meticulous Excavation by paying 2, returning Ugin's Nexus from the battlefield to your hand.
7. Repeat each turn.

This intricate loop turns a harmless artifact into a lethal engine for infinite turns by exploiting how its replacement effects interact with land status. With Toph, the First Metalbender transforming your nontoken artifacts into lands, Ugin's Nexus gains the card type it needs to be sacrificed to Coastal Hornclaw. When Ugin's Nexus heads to the graveyard, its own replacement effect exiles it instead and queues up an extra turn, which Toph's earthbend trigger immediately intercepts to return the Nexus safely to the battlefield. Finally, Meticulous Excavation allows you to neatly loop the Nexus back to your hand for reuse, ensuring the extra turns keep flowing indefinitely.