Athreos, Shroud-Veiled, Ugin's Nexus, Karn, Silver Golem, Master Transmuter, and Phyrexian Altar

Prerequisites

• Athreos, Shroud-Veiled on the battlefield
• Ugin's Nexus on the battlefield
• Karn, Silver Golem on the battlefield
• Master Transmuter on the battlefield
• Phyrexian Altar on the battlefield
• Master Transmuter does not have summoning sickness
• the first turn, with available each extra turn available

Steps

1. Activate Karn by paying , causing Ugin's Nexus to become an artifact creature until end of turn
2. At the beginning of your end step, Athreos' second ability triggers, putting a coin counter on Ugin's Nexus
3. Activate Phyrexian Altar by sacrificing Ugin's Nexus, adding
4. Ugin's Nexus is exiled instead of being put into your graveyard, causing you to take an extra turn after this one
5. Athreos' third ability triggers, causing you to return Ugin's Nexus from exile to the battlefield
6. Activate Master Transmuter by paying , tapping it and returning Ugin's Nexus to your hand, choosing to not put an artifact onto the battlefield
7. Move to your extra turn
8. Cast Ugin's Nexus by paying
9. Repeat

Results

• Infinite turns