Dark corners are good for little outside of collecting cobwebs, especially where walls meet ceilings up and out of reach inside of homes.
Thus this imminently practical glowing triangle by Peter Bristol that ”seems to blend-in and stand-out simultaneously.”
For stability, a steel bracket attaches is mounted to the wall itself. For easy bulb switching, magnets hold the fabric diffuser on the front. The final shape both breaks and completes the corner, though the draped cord is neither here nor there.