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

Toph, the First Metalbender

Ugin's Nexus

Meticulous Excavation

Phantom Train

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

This clever setup exploits Ugin's Nexus and its replacement effect by using Toph, the First Metalbender to seamlessly transform the artifact into a land, allowing its destruction to count as a death that triggers its exile-and-extra-turn clause. Once Ugin's Nexus is safely in exile, Toph's earthbend trigger immediately returns it to the battlefield, ready to be bounced back to your hand using Meticulous Excavation's ability. Meanwhile, Phantom Train acts as the sacrifice outlet that bypasses the graveyard entirely, ensuring the loop can be repeated indefinitely to take infinite turns and lock your opponents out of the game.