A disco ball appears, hovering where you designate. Light that is invisible hits the ball from all sides all the time; the light becomes visible when it is reflected off the ball. The ball can be caused to move location at will; you just have to concentrate for a second. The ball can spin in whatever pattern you want. You can change the color of the light, turn it on and off, etc. You can only ever have one disco ball at a time. It stays until dismissed or until you die, whichever happens first.