Progenitor Mimic + Time Walk + Shipwreck Dowser

Progenitor Mimic

Time Walk

Shipwreck Dowser

How it works

1. Cast Time Walk by paying its mana cost, taking an extra turn after this one.
2. At the beginning of your next upkeep, Progenitor Mimic triggers, creating a token copy of Shipwreck Dowser.
3. When the token Shipwreck Dowser enters the battlefield, it triggers itself, returning Time Walk from your graveyard to your hand.
4. Repeat.