Medomai the Ageless, Idris, Soul of the TARDIS, Thrummingbird, and Ashnod's Transmogrant

Prerequisites

• Medomai the Ageless on the battlefield
• Idris, Soul of the TARDIS in hand
• Thrummingbird on the battlefield
• Ashnod's Transmogrant on the battlefield
• An opponent cannot block creatures you control
• available

Steps

1. Activate Ashnod's Transmogrant by tapping and sacrificing it, putting a +1/+1 counter on Medomai the Ageless and causing it to become an artifact
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. Deal combat damage to an opponent using Idris and Thrummingbird
9. Idris and Thrummingbird trigger
10. Resolve the Idris trigger, causing you to take an extra turn after this one
11. Resolve the Thrummingbird trigger, putting a time counter on Idris
12. Repeat from step 6

Results

• Infinite turns