Merieke Ri Berit, and Thornbite Staff

Prerequisites

• Merieke Ri Berit on the battlefield
• Thornbite Staff on the battlefield
• Merieke Ri Berit does not have summoning sickness
• Thornbite Staff attached to Merieke Ri Berit
• You have a way to untap Merieke Ri Berit once

Steps

1. Activate Merieke Ri Berit's own ability by tapping it, gaining control of target creature as long as you control Merieke Ri Berit and creating a delayed triggered ability
2. Untap Merieke Ri Berit by any method
3. Merieke Ri Berit's delayed triggered ability triggers, destroying the creature you gained control of
4. Merieke Ri Berit's ability from Thornbite Staff triggers
5. In response, activate Merieke Ri Berit's own ability by tapping it, gaining control of target creature as long as you control Merieke Ri Berit and creating a delayed triggered ability
6. Resolve the ability from step 4, untapping Merieke Ri Berit
7. Repeat from step 3

Results

• Destroy any number of creatures
• Destroy each creature that enters the battlefield under an opponent's control