Progenitor Mimic + Skullwinder + Time Warp

Progenitor Mimic

Skullwinder

Time Warp

How it works

1. Cast Time Warp 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 Skullwinder.
3. When the token Skullwinder enters the battlefield, it triggers itself, returning Time Warp from your graveyard to your hand.
4. Repeat.