Progenitor Mimic + Eternal Witness + Time Stretch

Progenitor Mimic

Eternal Witness

Time Stretch

How it works

1. Cast Time Stretch by paying 8, taking two extra turns after this one.
2. At the beginning of your next upkeep, Progenitor Mimic triggers, creating a token copy of Eternal Witness.
3. When the token Eternal Witness enters the battlefield, it triggers itself, returning Time Stretch from your graveyard to your hand.
4. Repeat.