Felidar Guardian, Vesperlark, and Altar of Dementia

Prerequisites

• Felidar Guardian in hand
• Vesperlark on the battlefield
• Altar of Dementia on the battlefield
• available

Steps

1. Cast Felidar Guardian by paying
2. When Felidar Guardian enters the battlefield, it triggers, targeting Vesperlark
3. Holding priority, activate Altar of Dementia by sacrificing Felidar Guardian
4. Resolve the Felidar Guardian trigger, blinking Vesperlark
5. When Vesperlark leaves the battlefield, it triggers, returning Felidar Guardian from your graveyard to the battlefield
6. Repeat from step 2

Results

• Infinite ETB
• Infinite LTB
• Infinite mill
• Infinite sacrifice triggers
• Infinite self-mill
• Infinite death triggers