Ertha Jo, Frontier Mentor, Clock of Omens, Pheres-Band Tromper, and Encroaching Mycosynth

Prerequisites

• Ertha Jo, Frontier Mentor on the battlefield
• Clock of Omens on the battlefield
• Pheres-Band Tromper on the battlefield
• Encroaching Mycosynth on the battlefield

Steps

1. Activate Clock of Omens by tapping it and Pheres-Band Tromper, targeting Pheres-Band Tromper
2. Ertha Jo triggers, copying Clock of Omens' ability, targeting Clock of Omens
3. Resolve both Clock of Omens abilities, untapping it and Pheres-Band Tromper
4. Pheres-Band Tromper triggers, putting a +1/+1 counter on it
5. Repeat

Results

• Infinite +1/+1 counters on a creature