Kotis, Sibsig Champion + Altar of Dementia + Scholar of the Ages

Kotis, Sibsig Champion

Altar of Dementia

Scholar of the Ages

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 Scholar of the Ages, causing you to mill cards equal to Scholar of the Ages's power.
4. Cast Scholar of the Ages 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 Scholar of the Ages enters the battlefield, it triggers, returning the extra turn spell from your graveyard to your hand.
6. Repeat.