Mechanics first. Does its Agonizing Strike deal +1d6 or +2d6 nonlethal? You have both included, and the stat block (+1d6) generally trumps the text block.
Its Marrow Wring ability is nasty. Can the damage (and disability) be healed with regular magic? Does the condition disappear when the damage heals naturally? Or is it a permanent disability?
Given its 12 Str, why does it have a +2 melee damage bonus? And a +3 melee attack bonus? Is that just one of those times you changed its stats without adjusting its ability scores? ;)
Cry of Agony- a standard action? A free action?
Okay, I think I'm done criticizing. It's an awesome undead. Really creepy- almost Silent Hill creepy. Your description of a creature which, while it has bones, doesn't really care to retain its original skeletal integrity, really sets my skin a-crawlin'. Its fear-producing ability is almost redundant in my mind- it's already gonna scare the heck out of me as a player. And the fact that it really just wants to grab me and tear me limb from limb, that doesn't help.
My girlfriend's running a horror game. I'll send this off to her and see if she's interested in incorporating it. Going with your usual policy, I'll tell you how it massacres the party. ;)