Abuelo, Ancestral Echo, Ugin's Nexus, and Mirrorworks

Prerequisites

• Abuelo, Ancestral Echo on the battlefield
• Ugin's Nexus on the battlefield
• Mirrorworks on the battlefield
• available the first turn, with available each extra turn available

Steps

1. Activate Abuelo by paying , exiling Ugin's Nexus until the beginning of the next end step
2. At the beginning of your end step, Abuelo triggers, returning Ugin's Nexus from exile to the battlefield
3. When Ugin's Nexus enters the battlefield, Mirrorworks triggers, causing you to pay to create a token copy of Ugin's Nexus
4. Put the token Ugin's Nexus into exile due to the legend rule and its replacement effect, causing you to take an extra turn after this one
5. Activate Abuelo by paying , exiling Ugin's Nexus until the beginning of the next end step
6. Move to your next turn, not skipping it as Ugin's Nexus is not on the battlefield
7. Repeat from step 2

Results

• Infinite turns