Prototype Portal + Coretapper + Magistrate's Scepter

Prototype Portal

Coretapper

Magistrate's Scepter

How it works

1. Activate Magistrate's Scepter by tapping and removing three charge counters from it, taking an extra turn after this one.
2. Activate Prototype Portal by paying 2 and tapping it, creating a copy of Coretapper.
3. Move to your next turn.
4. Activate Coretapper's first ability by tapping it, putting a charge counter on Magistrate's Scepter.
5. Activate Coretapper's second ability by sacrificing it, putting two charge counters on Magistrate's Scepter.
6. Repeat.