Apollo was wandering the earth, searching for a suitable site to establish an oracle. Upon asking the nymph Telphusa at Boeotia, he was informed that Parnassus would be an auspicious spot (since she was afraid of competition and was attempting to lead him astray). So, Apollo went on to the craggy mountains of Parnassus and found a cavern in the rock there. Declaring the spot to be good, Apollo, aided by the legendary builders Trophonius and Agamedes and the local tribes, erected a lavish temple to himself from which he could dispense wisdom and unfailing advice.

However, a large and dangerous dragon lived nearby, who terrorized the animals and people of the countryside. Apollo slew it by the Castalian Spring and left itscorpse to rot, naming it "Pytho" from the Greek word "to rot". Next, Apollo buried the nymph Telphusa beneath a cliff and built a small shrine to himself there, since the nymph had tricked him into settling in a dragon infested location.

Apollo's work was not yet complete. He needed to find priests for his temple. Catching site of a Cretan ship sailing in the nearby sea, Apollo changed himself into the form of a Dolphin, swam to the ship, and leaped on board. The sailors fell back in fear as Apollo guided the ship to Crisa (on the coast near Delphi). Upon arrival, he returned to his normal form of a handsome man and demanded that the sailors become priests in his temple.

The guilt of the dragon's death was still on Apollo's hands, so he traveled to Tempe in Thessaly beneath Mount Olympus to ritually purify himself from miasma, or blood-pollution. This act of cleansing was celebrated every eight years at Delphi and pilgrims journeyed to his temple so that Apollo might cleanse them as he had been cleansed.