Emeria Shepherd, Felidar Guardian, and Altar of Dementia

Prerequisites

• Emeria Shepherd on the battlefield
• Felidar Guardian in hand
• Altar of Dementia on the battlefield
• You control Plains
• available

Steps

1. Cast Felidar Guardian by paying
2. Felidar Guardian enters the battlefield, blinking Plains
3. Emeria Shepherd triggers
4. Holding priority, activate Altar of Dementia by sacrificing Felidar Guardian, causing target player to mill one card
5. Resolve the Emeria Shepherd trigger, returning Felidar Guardian from your graveyard to the battlefield
6. Repeat from step 2

Results

• Infinite ETB
• Infinite LTB
• Infinite mill
• Infinite sacrifice triggers