Kotis, Sibsig Champion + Altar of Dementia + Revolutionist

Kotis, Sibsig Champion

Altar of Dementia

Revolutionist

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