Osgir, the Reconstructor + Karn, the Great Creator + Ugin's Nexus + Skirge Familiar + Exalted Sunborn

Osgir, the Reconstructor

Karn, the Great Creator

Ugin's Nexus

Skirge Familiar

Exalted Sunborn

How it works

1. Activate Osgir by paying 5, tapping it and exiling Ugin's Nexus from your graveyard, creating four token copies of Ugin's Nexus.
2. Put three of the Ugin's Nexus tokens into exile due to the legend rule and their replacement effects, causing you to take three extra turns after this one.
3. Activate Karn's first loyalty ability by putting a loyalty counter on it, choosing to do nothing.
4. Move to your next extra turn.
5. Repeat from step 3 one additional time.
6. Activate Karn's second loyalty ability by removing two loyalty counters from it, returning Ugin's Nexus from exile to your hand.
7. Activate Skirge Familiar by discarding Ugin's Nexus.
8. Move to your last extra turn.
9. Repeat.

This intricate masterpiece locks down the game by weaponizing Ugin's Nexus's replacement effect to chain infinite extra turns. Osgir, the Reconstructor makes multiplies of the Nexus, while Exalted Sunborn doubles the resulting token output to generate an overwhelming surplus of extra turns. Meanwhile, Karn, the Great Creator reaches into exile to fetch the Nexus back whenever needed, and Skirge Familiar gracefully discards it to fuel your mana requirements.