Conduit of Worlds + Time Stretch + Shipwreck Dowser + Ashnod's Altar

Conduit of Worlds

Time Stretch

Shipwreck Dowser

Ashnod's Altar

How it works

1. Activate Ashnod's Altar by sacrificing Shipwreck Dowser, adding CC.
2. Cast Time Stretch by paying 8, causing you to take two extra turns after this one.
3. Move to your first extra turn.
4. Activate Conduit of Worlds by tapping it, causing you to pay 3 to cast Shipwreck Dowser from your graveyard.
5. When Shipwreck Dowser enters the battlefield, it triggers, returning Time Stretch from your graveyard to your hand.
6. Move to your second extra turn.
7. Repeat.