Ugin's Nexus + Esoteric Duplicator + Arcbound Ravager

Ugin's Nexus

Esoteric Duplicator

Arcbound Ravager

How it works

1. During your end step, activate Arcbound Ravager by sacrificing Ugin's Nexus.
2. Ugin's Nexus is exiled instead of being put into your graveyard, causing you to take an extra turn after this one.
3. Esoteric Duplicator triggers, causing you to pay 2 to create a token copy of Ugin's Nexus at the beginning of your next end step.
4. Resolve the Arcbound Ravager ability, putting a +1/+1 counter on it.
5. Move to your extra turn.
6. At the beginning of your end step, Esoteric Duplicator triggers, creating a token copy of Ugin's Nexus.
7. Repeat.