Sin, Unending Cataclysm + Body of Research + Sage of Hours Combo

Sage of Hours on the battlefield.

Body of Research in hand.

Sin in hand or in the command zone.

You have a way to kill a creature.

plus commander tax if applicable available

Cast Body of Research by paying , creating a 0/0 Fractal creature token and putting a number of +1/+1 counters on it equal to your deck size.

Cast Sin either from your hand or from the command zone by paying plus commander tax if applicable. As it enters, remove all the counters from the Fractal and put twice that many +1/+1 counters on Sin.

Kill Sin. When it dies, it second ability triggers, putting its counters on Sage of Hours and shuffling Sin into your library.

Activate Sage of Hours by removing all +1/+1 counters from it, causing you to get an extra turn for each five +1/+1 counters removed from it.

Lock

Significant turns