Ultimecia, Time Sorceress // Ultimecia, Omnipotent, Tetzin, Gnome Champion // The Golden-Gear Colossus, Thassa, Deep-Dwelling, and Encroaching Mycosynth

Prerequisites

• Ultimecia, Time Sorceress // Ultimecia, Omnipotent on the battlefield
• Tetzin, Gnome Champion // The Golden-Gear Colossus on the battlefield
• Thassa, Deep-Dwelling on the battlefield
• Encroaching Mycosynth on the battlefield

Steps

1. Declare The Golden-Gear Colossus as an attacker
2. It triggers, creating two 1/1 Gnome artifact creature tokens and transforming Ultimecia, Time Sorceress into Ultimecia, Omnipotent
3. Ultimecia, Omnipotent triggers, causing you to take an extra turn after this one
4. At the beginning of your end step, Thassa triggers, blinking Ultimecia, Omnipotent
5. It'll enter the battlefield as Ultimecia, Time Sorceress
6. When Ultimecia, Time Sorceress enters, it triggers, causing you to surveil 2
7. Repeat each turn

Results

• Infinite turns
• Lock