Shirei, Shizo's Caretaker, Coretapper, and Magistrate's Scepter

Prerequisites

• Shirei, Shizo's Caretaker on the battlefield
• Coretapper on the battlefield
• Magistrate's Scepter on the battlefield
• Coretapper does not have summoning sickness

Steps

1. Activate Coretapper's first ability by tapping it, putting a charge counter on Magistrate's Scepter
2. Activate Coretapper's second ability by sacrificing it
3. When Coretapper dies, Shirei triggers, creating a delayed triggered ability
4. Resolve Coretapper's ability, putting two charge counters on Magistrate's Scepter
5. Activate Magistrate's Scepter's second ability by tapping it and removing three charge counters from it, taking an extra turn after this one
6. At the beginning of your end step, Shirei's delayed ability from step 3 triggers, returning Coretapper from your graveyard to the battlefield
7. Repeat each turn

Results

• Infinite turns