>>23480453Different guy:
It's not a mummy.
It's a cursed sarcophagus covered in solid gold, with a "wrong" thing inside. Whether the thing is a mummy or not, it needs to manipulate things from inside the coffin, so it projects shadow arms. If you give it a body, the thing loses its "wrong" mystique and the arms have no purpose.
Related: Spiritomb is bound to the Odd Keystone as punishment. It would be just as weird if Spiritomb had a Mega Evolution where it grew arms and legs.
