Spreading Plague, Darkest Hour, and Eldrazi Monument

Prerequisites

• Spreading Plague on the battlefield
• Darkest Hour on the battlefield
• Eldrazi Monument on the battlefield

Steps

1. Whenever a creature enters the battlefield, Spreading Plague triggers, destroying all creatures, as they all black due to Darkest Hour
2. Because Eldrazi Monument gives your creatures indestructible, only your opponents' creatures are destroyed

Results

• Destroy all creatures opponents control whenever a creature enters the battlefield