Pan is the god of shepherds and their flocks, of the wild Arcadian mountains, and of rustic music, and he wears his wildness on his body: horns, a beard, and the shaggy legs and hooves of a goat. He belongs to the uplands of Arcadia rather than to the ordered city, and he haunts the noonday stillness of the hills. From him comes the word panic, the sudden, groundless terror that could seize flocks, or armies, in lonely places was attributed to the god's presence. His instrument is the syrinx or pan-pipe, and myth explains its origin: pursuing the nymph Syrinx, who was changed into reeds to escape him, Pan cut the reeds and bound them into the first shepherd's pipe.
Pan's formal introduction to Athens is unusually well documented for a Greek cult's origin. Herodotus reports that in 490 BCE, before the Battle of Marathon, the runner Pheidippides, sent to seek Spartan help, encountered Pan on the road in Arcadia; the god complained that Athens neglected him despite his goodwill and promised to aid the city in the coming fight. After the Athenian victory the city made good on the implied bargain, establishing a cult to Pan in a cave on the northwest slope of the Acropolis and instituting annual torch-races and sacrifices in his honour, a rare case in Greek religion where the founding of an urban cult is tied to a specific, datable historical event rather than to unrecorded prehistory.