I kinda don't get why this thing can't Shadow Claw simply because he doesn't have a claw. If that's the reasoning, then explain stuff like Slacking with Slash (I understand there's no way around it because of his preevos, but he does looks devoid of claws) or how about Dodrio with Steel Wing and Fly (imaginary wings?). It's not like he's using claws of his own for the attack, anyways. Just read the description closely:
It's a claw made from shadows, not imbued with them, and it does make sense for our mummy to control shadows and the like.
The user slashes with a sharp claw made from shadows. It has high critical hit ratio
It's a claw made from shadows, not imbued with them, and it does make sense for our mummy to control shadows and the like.