An immobile, cube-shaped prison composed of magical force springs into existence around an area you choose within range. The prison can be a cage or a solid box, as you choose.
You each side can be a maximum of 20 feet. This is small enough for most medium sized creatures to unable to escape. If this is reduced to 5 feet per side the chamber become impenetrable by any solid, liquid or gas.
A creature inside the cage can't leave it by nonmagical means. If the creature tries to use teleportation or interplanar travel to leave the cage, it must first make a Charisma saving throw. On a success, the creature can use that magic to exit the cage. On a failure, the creature can't exit the cage and wastes the use of the spell or effect. The cage also extends into the Ethereal Plane, blocking ethereal travel.
Any time before the end of the spell the caster can spend an action to collapse the cage causing 4d10 plus the caster's modifier. If there is a creature inside it must make a Con save at disadvantage. If it succeeds it takes half damage, full damage on a failed save. If the spell's duration ends naturally the chamber simply vanishes
* - (A drop of the caster's blood (-1 HP))