It will allow you to control the Z axis of your character. Which gives you the ability to make your character 'float' in the air or 'drop' below the ground. It works best with ranged characters (i.e. Hunters and Mages).
This would be best used to level your character. Find a good spot where the mobs continuously spawn then drop below the ground. If you do it in a good spot the mobs will not be able to attack you but you will be able to hit them.
