Lethal Vapors, and Phyrexian Revoker

Prerequisites

• Lethal Vapors on the battlefield
• Phyrexian Revoker on the battlefield
• "Lethal Vapors" chosen with Phyrexian Revoker

Steps

1. Whenever a creature enters the battlefield, Lethal Vapors triggers, destroying that creature
2. Because Phyrexian Revoker 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