Mirror of life trapping

A mirror of life trapping was a magical mirror that could be armed to trap creatures reflected by it in an extradimensional prison.

Description
Typical mirros of life trapping were made of crystal, measuring about in height and weighing. They were usually frame in wood or metal.

Powers
The mirror accepted a command word that activated or deactivated it. While active, anyone within of the mirror capable of seeing their own reflection in it risked being trapped in one of its twelve extradimensional cells. The cells were seemingly infinite spaces covered in fog, whose occupants did not age and did not require food, water, or sleep to survive. It was possible to escape the cells by planar travel.

If more than twelve creatures became trapped by the mirror, one of the prisoners was freed at random.

It was possible to communicate with the mirror's prisoners by calling their name while gazing at the mirror. The creature appeared as a normal reflection on the mirror, and communication could proceed normally. A second command word could be used to free one of the prisoners.

Notable Mirrors of Life Trapping
The Tomb of the Nine Gods contained a mirror of life trapping attached to the wall by sovereign glue.