Felidar Guardian, Altar of the Brood, and Clever Impersonator

Prerequisites

• Felidar Guardian on the battlefield
• Altar of the Brood on the battlefield
• Clever Impersonator in hand
• available

Steps

1. Cast Clever Impersonator by paying
2. Clever Impersonator 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 Clever Impersonator'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 Clever Impersonator
8. Repeat from step 2

Results

• Infinite ETB
• Infinite LTB
• Infinite mill