Zoroastrian sources call Alexander gizistag, the accursed, a title he receives in no other tradition. The Middle Persian books — the Denkard, the Arda Viraf Namag and the Letter of Tansar — hold that he burned the archetype copy of the Avesta, written in gold on prepared ox hides and kept at Persepolis, and killed the priests who carried the remainder in memory, so that the transmission was broken in both its written and oral forms. What survives, on this account, is a partial reassembly made under the Arsacids and completed under the Sasanians, and the tradition itself says the Avesta as it now exists is a fraction of what existed — the Denkard summarises twenty-one nasks, of which only one, the Vendidad, survives complete. Historians treat the burning account cautiously: Persepolis certainly burned in 330 BCE, but whether a written Avesta existed then at all is contested, since the Avestan alphabet appears to be a Sasanian invention. The story is nonetheless what the tradition believes about its own losses, and the losses are real.