Add Shadow Claw, Don't Add Shadow Bone
Shadow Claw is a sufficient buff; Shadow Bone's additional power and useful secondary effect would be gratuitous.
As an aside, I don't really understand why the slate isn't "Add Shadow Claw, Don't Add Shadow Bone" vs "Add Shadow Bone." Shadow Bone is the superior move in all competitive aspects, so Shadow Claw would be a flavor move, at most, if Shadow Bone were present in Revenankh's movepool.