Prototype Portal, Ugin's Nexus, and Umbral Collar Zealot

Prerequisites

• Prototype Portal on the battlefield
• Ugin's Nexus in exile
• Umbral Collar Zealot 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 Umbral Collar Zealot by acrificing the Ugin's Nexus token
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. Resolve the Umbral Collar Zealot ability Repeat each turn

Results

• Infinite turns