Prototype Portal, Ugin's Nexus, and Krark-Clan Ironworks

Prerequisites

• Prototype Portal on the battlefield
• Ugin's Nexus in exile
• Krark-Clan Ironworks on the battlefield
• each turn available

Steps

1. Activate Prototype Portal by paying and tapping it, creating a token copy of Ugin's Nexus
2. Activate Krark-Clan Ironworks by sacrificing the Ugin's Nexus token, adding
3. The Ugin's Nexus token is exiled instead of being put into your graveyard, causing you to take an extra turn after this one
4. Repeat each turn

Results

• Infinite turns