Ertha Jo, Frontier Mentor, Clock of Omens, Siren of the Silent Song, and Encroaching Mycosynth

Prerequisites

• Ertha Jo, Frontier Mentor on the battlefield
• Clock of Omens on the battlefield
• Siren of the Silent Song on the battlefield
• Encroaching Mycosynth on the battlefield

Steps

1. Activate Clock of Omens by tapping it and Siren of the Silent Song, targeting Siren of the Silent Song
2. Ertha Jo triggers, copying Clock of Omens' ability, targeting Clock of Omens
3. Resolve both Clock of Omens abilities, untapping it and Siren of the Silent Song
4. Siren of the Silent Song triggers, causing each opponent to discard and mill a card
5. Repeat

Results

• Infinite mill