Kotis, Sibsig Champion + Altar of Dementia + Warden of the Eye

Kotis, Sibsig Champion

Altar of Dementia

Warden of the Eye

How it works

1. Cast the extra turn spell by paying its mana cost, causing you to take an extra turn after this one.
2. Move to your extra turn.
3. Activate Altar of Dementia by sacrificing Warden of the Eye, causing you to mill cards equal to Warden of the Eye's power.
4. Cast Warden of the Eye from your graveyard by paying its mana cost and exiling three other cards from your graveyard, ensuring not to exile the extra turn spell.
5. When Warden of the Eye enters the battlefield, it triggers, returning the extra turn spell from your graveyard to your hand.
6. Repeat.