Osgir, the Reconstructor, Karn, the Great Creator, Ugin's Nexus, Witch-king of Angmar, and Primal Vigor

Prerequisites

• Osgir, the Reconstructor on the battlefield
• Karn, the Great Creator on the battlefield
• Ugin's Nexus in the graveyard
• Witch-king of Angmar on the battlefield
• Primal Vigor on the battlefield
• available, with an additional every fourth turn available

Steps

1. Activate Osgir by paying , 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 Witch-king of Angmar by discarding Ugin's Nexus
8. Move to your last extra turn
9. Repeat

Results

• Infinite turns