Doctor M said:While I agree that they should have gone for an artifact or something more embedded into the collective unconscious (a REAL City of Gold, the original Cross, the Fate of Atlantis, the Infernal Machine, proof aliens built the pyrmaids, the last lightsaber (it did happen a LONG time ago)...), the mythology of 13 crystal skulls was not invented for Indy. It's just more obscure.
Really, seriously? Wow, I had no idea. And I'm a Huge Nerd.