Bone Maiden

A target in range must succeed a Charisma Saving Throw or be banished inside an iron maiden formed of bone that appears in its space. They are considered restrained and incapacitated, immune to all damage coming from the outside, and take 2d6 piercing damage at the start of each of their turn, as spikes of bones dig in their body. At the end of each of its turns a trapped creature can repeat the saving throw, escaping on a success. The bone maiden has AC 13, 80 hit point, immunity to psychic and poison damage, an vulnerability to bludgeoning damage. If the maiden is destroyed the creature trapped inside is freed.