Aminatou, the Fateshifter, Spark Double, and Altar of the Brood

Prerequisites

• Aminatou, the Fateshifter on the battlefield
• Spark Double on the battlefield
• Altar of the Brood on the battlefield

Steps

1. Activate Aminatou's second loyalty ability by removing a loyalty counter from it, blinking Spark Double
2. Spark Double enters the battlefield as a non-legendary copy of Aminatou
3. Altar of the Brood triggers, causing each opponent to mill one card
4. Activate Spark Double's second loyalty ability by removing a loyalty counter from it, blinking Aminatou
5. Aminatou enters the battlefield, triggering Altar of the Brood, causing each opponent to mill one card
6. Repeat

Results

• Infinite ETB
• Infinite LTB
• Infinite mill