Mimic Vat + Coretapper + Magistrate's Scepter

Mimic Vat

Coretapper

Magistrate's Scepter

How it works

1. Activate Mimic Vat by paying 3 and tapping it, creating a token copy of Coretapper with haste that will be exiled at the beginning of the next end step.
2. Activate Coretapper's first ability by tapping it, putting a charge counter on Magistrate's Scepter.
3. Activate Coretapper's second ability by sacrificing it, putting two charge counters on Magistrate's Scepter.
4. Activate Magistrate's Scepter's second ability by tapping it and removing three charge counters from it, taking an extra turn after this one.
5. At the beginning of the end step, the delayed ability from Mimic Vat triggers, failing to exile anything.
6. Repeat each turn.