Requires

Felidar Guardian must be in hand. Vesperlark must be on the battlefield. Altar of Dementia must be on the battlefield. Mana needed:

Steps

1. Cast Felidar Guardian by paying .
2. When Felidar Guardian enters the battlefield, it triggers.
3. In response, activate Altar of Dementia by sacrificing Felidar Guardian, causing target player to mill one card.
4. Resolve Felidar Guardian's ability, blinking Vesperlark.
5. When Vesperlark leaves the battlefield, its ability triggers, returning Felidar Guardian from your graveyard to the battlefield.
6. Repeat from step 2.

Results