Scute Mob + Bioshift + Sage of Hours + Isochron Scepter

Scute Mob

Bioshift

Sage of Hours

Isochron Scepter

How it works

1. Activate Isochron Scepter by tapping it and paying 2, casting a copy of Bioshift without paying its mana cost, targeting Scute Mob and Sage of Hours.
2. Sage of Hours triggers, putting a +1/+1 counter on itself.
3. Resolve the Bioshift copy, moving four +1/+1 counters from Scute Mob onto Sage of Hours.
4. Activate Sage of Hours by removing all +1/+1 counters from it, generating an extra turn after this one.
5. At the beginning of your extra turn's upkeep, Scute Mob triggers, putting four +1/+1 counters on itself.
6. Repeat.

This clever loop turns a modest bug into a time-bending engine by constantly recycling instant-speed counter manipulation. Isochron Scepter does the heavy lifting by repeatedly casting Bioshift for a mere two mana, which not only moves four accumulated counters from Scute Mob onto Sage of Hours, but also triggers Sage of Hours's heroic ability to safely stack up the necessary counter total. Once Sage of Hours has enough counters, you strip them away to take an extra turn, allowing Scute Mob's upkeep trigger to naturally restock your counter supply so the cycle can begin anew.