Cube of Interrogation

20 food cube of dark grey smoke forms in an area you designate and remains stationary for the duration. you and a creature of medium size you designate may enter the cube. Once you enter, the doorway made of light grey smoke turns dark to match the rest of the cube. inside the cube is a singular chair which forms from the same grey light as the doorway, it will grapple your target and chain them to its surface. once you enter no entity can see into the cube from the outside and no sound passes through its walls walls