Man, now that's an interesting monster. All the information I could find was very vague about the appearance and lifestyle of the monster. Did you find some source of more myths somewhere, or is the detail from artistic liberty?

I think the damage mod on your attacks is off. Unarmed strikes are light weapons, my math says it should be +7. The thrown rocks aren't normally two-handed weapons, so they should be +7 as well. The melee attack should be +12 as far as I know.
You misspelled nonlethal a few times in there.

The Acheri looks good!
Init should be +6, if my math is right.
I think the attack mod on the claws should be +4. I think incorporeal undead use their dex for attack automatically.
CMB should be +2. CMD has no +, it's a static number and I think it's supposed to be 14.
Other than that, I see no problems. certainly a creepy monster, and I like that there's a specific way to kill it for good, like a vampire or a lich.
I could see a low-level party having to go out to the graveyard to put one down for good.