Magistrate's Scepter + Coretapper + Helm of the Host

Magistrate's Scepter

Coretapper

Helm of the Host

How it works

1. At the beginning of combat on your turn, Helm of the Host triggers, creating a token copy of Coretapper with haste.
2. Activate the token Coretapper's first ability by tapping it, putting a charge counter on Magistrate's Scepter.
3. Activate the token 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, causing you to take an extra turn after this one.
5. Repeat each turn.