Chainer, Nightmare Adept, Coretapper, and Magistrate's Scepter

Prerequisites

• Chainer, Nightmare Adept on the battlefield
• Coretapper on the battlefield
• Magistrate's Scepter on the battlefield
• Coretapper does not have summoning sickness
• each turn available

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, putting two charge counters on Magistrate's Scepter
3. Activate Magistrate's Scepter's second ability by tapping it and removing three charge counters from it, taking an extra turn after this one
4. During your next extra turn's main phase, activate Chainer by discarding a card, allowing you cast Coretapper from your graveyard this turn
5. Cast Coretapper by paying
6. When Coretapper enters the battlefield, Chainer triggers, giving Coretapper haste until your next turn
7. Repeat each turn

Results

• Infinite turns