Emry, Lurker of the Loch + Ugin's Nexus + Isochron Scepter + Pull from Eternity + Umbral Collar Zealot

Emry, Lurker of the Loch

Ugin's Nexus

Isochron Scepter

Pull from Eternity

Umbral Collar Zealot

How it works

1. Activate Umbral Collar Zealot by sacrificing Ugin's Nexus
2. When Ugin's Nexus is sacrificed, it is exiled instead of being put into your graveyard, causing you to take an extra turn after this one.
3. Move to your next turn.
4. Activate Isochron Scepter by paying 2 and tapping it, casting a copy of Pull from Eternity without paying its mana cost.
5. Resolve Pull from Eternity, putting Ugin's Nexus from exile into your graveyard.
6. Activate Emry by tapping it, targeting Ugin's Nexus.
7. Cast Ugin's Nexus from your graveyard by paying 5.
8. Repeat.

This intricate loop locks down infinite turns by weaponizing Ugin's Nexus's replacement effect, which normally prevents extra turns entirely. By using Umbral Collar Zealot to sacrifice the Nexus, you bypass its death trigger and instead send it to exile while successfully triggering its extra turn reward. From there, Isochron Scepter casts Pull from Eternity to pluck the Nexus right back out of exile and into the graveyard, where Emry, Lurker of the Loch can recast it back onto the battlefield.