The tablets themselves are twelve engraved pieces of black jade inscribed by Zanthu, a wizard and high priest of Ythogtha. They are written in a hieratic form of Naacal, the language of the sunken continent of Mu. The tablets reveal a partial history of Mu, describing Zanthu's struggle against the rising cult of Ghatanothoa and his own religion's lamented decline. He also describes his failed attempt to release the god Ythogtha from its prison. Upon witnessing three black, beaked, slimy heads, "vaster than any mountain", rising from a gorge, he flees in terror when he realizes that they are merely the god's fingertips. According to Zanthu, he and some of his people escaped the destruction of Mu, which was sunk by the wrath of the Elder Gods.