Cavalier of Night + Mirror Image + Altar of Dementia

Cavalier of Night

Mirror Image

Altar of Dementia

How it works

1. Activate Altar of Dementia by sacrificing Mirror Image.
2. When Mirror Image dies, its last ability from Cavalier of Night triggers, returning itself from your graveyard to the battlefield as a copy of Cavalier of Night.
3. When Mirror Image enters the battlefield, its first triggered ability from Cavalier of Night triggers; choose not to sacrifice a creature.
4. Resolve the Altar of Dementia ability from step 1.
5. Repeat.