Prowling Geistcatcher + Karmic Guide + Altar of Dementia

Prowling Geistcatcher

Karmic Guide

Altar of Dementia

How it works

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.