Progenitor Mimic + Mnemonic Wall + Time Walk

Progenitor Mimic

Mnemonic Wall

Time Walk

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 Mnemonic Wall.
3. When the token Mnemonic Wall enters the battlefield, it triggers itself, returning Time Walk from your graveyard to your hand.
4. Repeat.