Glass Cube Pendant

Once per day this pendant allows you to create a
15-foot-square hollow cube of glass in an area
you can see. If a creature is in the area where the cube forms, it escapes with a successful DEX
save. Creatures that fail are trapped in the cube. The cube has AC 14 and 200 hit points. It is immune to acid, necrotic, poison and psychic damage, but is vulnerable to force and thunder. Creatures inside the cube when it is destroyed take 8d6 slashing damage from glass shards.