Felidar Guardian, Altar of the Brood, and Spark Double

Prerequisites

• Felidar Guardian on the battlefield
• Altar of the Brood on the battlefield
• Spark Double in hand
• available

Steps

1. Cast Spark Double by paying
2. Spark Double enters the battlefield as a copy of Felidar Guardian, triggering Altar of the Brood and itself
3. Resolve the Altar of the Brood trigger, causing each opponent to mill a card
4. Resolve the Spark Double's trigger, blinking Felidar Guardian
5. Felidar Guardian enters the battlefield, triggering Altar of the Brood and itself
6. Resolve the Altar of the Brood trigger, causing each opponent to mill a card
7. Resolve the Felidar Guardian's trigger, blinking Spark Double
8. Repeat from step 2

Results

• Infinite ETB
• Infinite LTB
• Infinite mill