Lethal Vapors, Encroaching Mycosynth, and Collector Ouphe

Prerequisites

• Lethal Vapors on the battlefield
• Encroaching Mycosynth on the battlefield
• Collector Ouphe on the battlefield

Steps

1. Whenever a creature enters the battlefield, Lethal Vapors triggers, destroying that creature
2. Because Collector Ouphe prevents Lethal Vapors's activated ability from being activated, it cannot be destroyed due to its ability

Results

• Destroy all creatures that enter the battlefield