Magistrate's Scepter + Energy Chamber + Tawnos, Urza's Apprentice

Magistrate's Scepter

Energy Chamber

Tawnos, Urza's Apprentice

How it works

1. Activate Magistrate's Scepter, removing 3 charge counters to take an extra turn.
2. Activate Tawnos, copying the extra turn ability.
3. Pass the turn.
4. At the beginning of your upkeep, Energy Chamber triggers, putting a charge counter on Magistrate's Scepter.
5. Activate Magistrate's Scepter, putting a charge counter on itself.
6. Activate Tawnos, copying the trigger.
7. Pass the turn.
8. Repeat.