Medomai the Ageless, Idris, Soul of the TARDIS, Karn's Bastion, and Neurok Transmuter

Prerequisites

• Medomai the Ageless on the battlefield
• Idris, Soul of the TARDIS in hand
• Karn's Bastion on the battlefield
• Neurok Transmuter on the battlefield
• An opponent cannot block creatures you control
• available the first turn, with each extra turn available

Steps

1. Activate Neurok Transmuter's first ability by paying , causing Medomai the Ageless to become an artifact until end of turn
2. Deal combat damage to an opponent using Medomai the Ageless
3. Medomai the Ageless triggers, causing you to take an extra turn after this one
4. Cast Idris by paying
5. When Idris enters the battlefield, it triggers, exiling Medomai the Ageless until Idris leaves the battlefield
6. Move to your extra turn
7. At the beginning of your upkeep, Idris's vanishing ability triggers, removing a time counter from it
8. Activate Karn's Bastion's second ability by paying and tapping it, putting a time counter on Idris
9. Deal combat damage to an opponent using Idris
10. Idris triggers, causing you to take an extra turn after this one
11. Repeat from step 6

Results

• Infinite turns