Muldrotha, the Gravetide + Ugin's Nexus + Isochron Scepter + Pull from Eternity + Umbral Collar Zealot

Muldrotha, the Gravetide

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. Cast Ugin's Nexus from your graveyard by paying 5.
7. Repeat.