Crystal Skulls
The Crystal Skulls are Pieces of Eden, created by Those Who Came Before. They were scattered throughout Central America, coming into the possession of Aztec and Mayan tribes. They are mentioned briefly in one of Warren Vidic's emails in Assassin's Creed. In 1520, Giovanni Borgia, an Assassin and member of Hernán Cortés' crew, managed to steal one from an Aztec priest in Tenochtitlan. Upon returning to Europe, he took it to Bombastus, who was an expert in studying the Pieces of Eden. [1]
Mitchell-Hedges-Skull
Several of the skulls did presumably come into possession of Abstergo, as Alan Rikkin notes in an email to Vidic that the Mitchell-Hedges Communicators work. Hence it is assumed that the power of the Crystall Skulls is used as a form of communication with each other. Therefore, Abstergo intended to to use them as a safe communication system. [2]