Eldritch Cube

A black, nonreflective, incorporeal 10 ft cube appears in an unoccupied space that you can see. Its space can be in midair i you so desire. When a creature starts it turn in the cube or enters the cube for the first time on its turn it must make a intelligence saving throw, taking 5d6 psychic damage  on a failed save, or half damage on a successful save.

As a bonus action, you can move the cube up to 10 ft in any direction to a space you can see. The cube cannot be made to pass through other creatures in this way.