The Wish stone is a powerful object that can only be created by the gods, or the wish spell. If the Wish spell is cast and the casters create the only magic item that when used can cast the wish spell without enduring the stress or the spell slots. Now when creating it the caster does not have any kinds of stress that the wish spell places, for you are just trapping the spell in the stone. Now when released the stone takes all the stress and is destroyed. You can also make as many as you want with the number of wish spells equal to the amount that you want to make, also you can't use a wish stone to create more wish stones. The stone would burst and cause you 150 (10d20 + 50) force/physic damage (DM choice). If you were to die from that your soul would be lost forever as well as your body (for you have torn a hole in magic).