Progenitor Mimic + Time Stretch + Revolutionist

Progenitor Mimic

Time Stretch

Revolutionist

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

This looping extra-turn engine leverages Progenitor Mimic as a tireless copy machine, targeting Revolutionist to continuously recycle your spells. When the non-token Progenitor Mimic spawns a fresh token copy of Revolutionist during your upkeep, Revolutionist's enters-the-battlefield trigger grabs Time Stretch right back out of your graveyard and puts it into your hand. From there, you simply cast Time Stretch to chain consecutive extra turns indefinitely, locking your opponents out of the game entirely.