Magistrate's Scepter + Coretapper + Umbral Mantle

Magistrate's Scepter

Coretapper

Umbral Mantle

How it works

1. Activate Coretapper's first ability by tapping it, putting a charge counter on Magistrate's Scepter.
2. Activate Coretapper by paying 3 and untapping it, giving it +2/+2 until end of turn.
3. Repeat from step 1 one additional time.
4. Activate Coretapper's first ability by tapping it, putting a charge counter on Magistrate's Scepter.
5. Activate Magistrate's Scepter's second ability by tapping and removing three charge counters from it, causing you to take an extra turn after this one.
6. Repeat each turn.