Reaper King, Overseer of the Damned, and Conspiracy

Prerequisites

• Reaper King on the battlefield
• Overseer of the Damned on the battlefield
• Conspiracy on the battlefield
• You have a way to cause a creature to enter the battlefield
• "Scarecrow" chosen with Conspiracy

Steps

1. Cause a creature to enter the battlefield
2. Reaper King triggers, destroying target nontoken creature an opponent controls
3. The creature dies, triggering Overseer of the Damned, creating a 2/2 Zombie creature token
4. The Zombie enters the battlefield as a Scarecrow due to Conspiracy, triggering Reaper King, destroying target nontoken creature an opponent controls
5. Repeat from step 3
6. This loop will also repeat whenever another creature enters the battlefield under your control

Results

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