Mirror of Life Trapping, and Containment Priest

Prerequisites

• Mirror of Life Trapping on the battlefield
• Containment Priest on the battlefield

Steps

1. Whenever a nontoken creature enters that was cast, Mirror of Life Trapping triggers, exiling that creature
2. Whenever a nontoken creature enters that wasn't cast, it is instead exiled due to Containment Priest
3. This also applies to any creatures that would be put onto the battlefield by Mirror of Life Trapping

Results

• Exile all nontoken creatures that enter the battlefield
• Lock