Artificial Evolution, Erratic Portal, Medomai the Ageless, and Preeminent Captain

Prerequisites

• Artificial Evolution in hand
• Erratic Portal on the battlefield
• Medomai the Ageless on the battlefield
• Preeminent Captain on the battlefield
• Medomai and Preeminent Captain does not have summoning sickness
• Opponents can not block and kill Preeminent Captain and Medomai
• available

Steps

1. Cast Artificial Evolution by paying , changing all instances of "Soldier" on Preeminent Captain to "Sphinx"
2. Declare Preeminent Captain as an attacker
3. Preeminent Captain triggers, putting Medomai from your hand onto the battlefield tapped and attacking
4. Deal combat damage with Medomai, causing you to take an extra turn after this one
5. Activate Erratic Portal by paying and tapping it, returning Medomai to your hand
6. Pass the turn
7. Repeat from step 2

Results

• Infinite turns