Reveillark + Activated Sleeper + Altar of Dementia

Reveillark

Activated Sleeper

Altar of Dementia

How it works

1. Activate Altar of Dementia by sacrificing Reveillark.
2. When Reveillark dies, it triggers, returning Activated Sleeper from your graveyard to the battlefield as a copy of Reveillark.
3. Activate Altar of Dementia by sacrificing Activated Sleeper.
4. When Activated Sleeper dies, it triggers, returning Activated Sleeper from your graveyard to the battlefield as a copy of Reveillark.
5. Resolve the Altar of Dementia ability, causing target player to mill cards equal to Activated Sleeper's power.
6. Repeat from step 3.