Azi Dahaka appears in the Avesta as the most formidable of the created evils, a three headed, three jawed, six eyed serpent whose name simply means dragon, Dahaka. The Aban Yasht, the hymn to the waters and to the goddess Anahita collected as Yasht 5, has the hero Thraetaona pray to her for the strength to overcome him, and the same hymn credits Azi Dahaka himself with seeking her favor first, for power to depopulate the world of its people, a request the text has Anahita refuse. Thraetaona ultimately defeats the creature, though later tradition holds he does not kill it outright but binds it, commonly located at Mount Damavand in later Persian geography, where it is said to remain chained until it breaks free at the end of days as one of the final evils the world must face before its renewal.
The creature functions in Avestan cosmology as druj incarnate, the Lie given monstrous form, set against Ahura Mazda's order the way every major demon in the Zoroastrian scheme personifies a specific corruption of a specific good. Azi Dahaka's association with drought, death and the extinguishing of legitimate kingship recurs through the textual tradition and carries directly into the creature's later, far more famous incarnation.