It depend on how one interprets the word "weapon" in the items entry, if you view weapon as meaning an object used to injure, defeat, or destroy (as I believe is probably intended) then I do not think it would protect against Natural Attacks or Unarmed Strikes but if you view weapon as meaning the thing upon which the damage from one's attacks is based then you could consider Natural Attacks or Unarmed Strikes to be weapons and then the Starmantle Cloak would protect against them unless they were magical.