Mirror of Life Trapping

This elaborate 50 pound mirror hides an extradimensional prison beneath its smooth, silvery surface. 

You can use an action to activate or deactivate the mirror by speaking its command word while within 5 feet. While active, when a creature other than you sees its reflection in the mirror while within 30 feet, it makes a DC 15 Charisma saving throw . Creatures that are aware of the mirror’s nature have advantage , and constructs automatically succeed. On a failure, the creature and all its possessions are trapped inside one of the mirror’s 12 extradimensional cells.

• Each extradimensional cell is an infinite plane filled with thick fog. Creatures trapped within do not need to eat, drink, or sleep, nor do they age.
• Creatures can escape via planar travel, but are otherwise trapped until freed.
• If a creature is trapped but the mirror’s cells are already full, a randomly determined trapped creature is freed so the new creature may be trapped. 
• While within 5 feet of the mirror, you can use an action to call forth a trapped creature. The creature appears in the surface of the mirror, allowing you and the creature to communicate normally.
• A trapped creature can be freed by using an action to speak a different command word. The creature appears in an unoccupied space near the mirror and facing away from it.

When the mirror (AC 11, 10 hit points, vulnerability to bludgeoning damage) is reduced to 0 hit points it shatters, freeing all trapped creatures. The creatures appear in unoccupied spaces nearby.