Osgir, the Reconstructor + Ugin's Nexus + Pull from Eternity + Isochron Scepter

Osgir, the Reconstructor

Ugin's Nexus

Pull from Eternity

Isochron Scepter

How it works

1. Activate Osgir by tapping it, paying 5, and exiling Ugin's Nexus from your graveyard, creating two token copies of Ugin's Nexus.
2. Put one of them into your graveyard due to the legend rule.
3. The token copy of Ugin's Nexus that was just put into your graveyard triggers, causing you to take an extra turn after this one.
4. Activate Osgir by paying 1 and sacrificing a token copy of Ugin's Nexus.
5. The sacrificed token copy of Ugin's Nexus triggers, causing you to take an extra turn after this one.
6. Osgir's ability resolves, giving target creature you control +2/+0 until end of turn.
7. Move to your next extra turn.
8. Activate Isochron Scepter by tapping it and paying 2, copying Pull from Eternity.
9. Cast Pull from Eternity, returning Ugin's Nexus to your graveyard.
10. Move to your next extra turn.
11. Repeat.