In a hymn of the Avesta incorporated by Ferdowsi in the Shahnameh, Tishtrya is involved in a cosmic struggle against the drought-bringing demon Apaosha.
Apaosa soon gained the upper hand over Tishtrya, who was weakened from the lack of sufficient prayers and sacrifices from humankind.
The yazata proceeded to call upon the creator, Ahura Mazda, who himself then intervened by offering a sacrifice to the overwhelmed god.
Infused with the power brought by this sacrifice, Tishtrya was able to overcome Apaosa and his rains were able to flow to the parched fields and pastures unabated by drought.
[citation needed] During the Hellenistic period, Tishtrya came to be associated with Pythian Apollo, patron of Delphi, and thus a divinity of oracles.