Prowling Geistcatcher, Karmic Guide, and Altar of Dementia

Prerequisites

• Prowling Geistcatcher on the battlefield
• Karmic Guide on the battlefield
• Altar of Dementia on the battlefield

Steps

1. Activate Altar of Dementia by sacrificing Karmic Guide
2. When Karmic Guide dies, Prowling Geistcatcher's first ability triggers, exiling Karmic Guide from your graveyard
3. Activate Altar of Dementia by sacrificing Prowling Geistcatcher
4. When Prowling Geistcatcher dies, its second ability triggers, returning Karmic Guide from exile to the battlefield
5. When Karmic Guide enters the battlefield, it triggers, returning Prowling Geistcatcher from your graveyard to the battlefield
6. Resolve the Altar of Dementia abilities from step 1 and step 3, causing target player to mill cards equal to Karmic Guide and Prowling Geistcatcher's power
7. Repeat

Results

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