The stone he put in its place looked almost exactly like Jon's stone, except that it wasn't. It was The Anger Stone.
It worked just like the normal stone, except that every time a wish was granted, the wisher became a little more angry. At first, the wisher may just be annoyed or irritated, but eventually he or she would become pissed off or even furious. And thus, the wisher's wishes in that state of mind would be filled with ill-content.
But the wisher wouldn't stay angry forever. If the wisher waited for 4 hours after his or her wish, before making another wish, then his or her anger would dissipate completely. The wisher will realize what he or she had wished for, but won't be able to fix anything, because like the regular stone, wishes couldn't be reversed.
