Merieke Ri Berit, and Intruder Alarm

Prerequisites

• Merieke Ri Berit on the battlefield
• Intruder Alarm on the battlefield
• Merieke Ri Berit does not have summoning sickness

Steps

1. Tap Merieke Ri Berit to gain control of target creature
2. Have a creature enter the battlefield
3. Merieke Ri Berit untaps, repeat loop

Results

• Destroy any creature whenever a creature enters the battlefield