The principle source of information on the figure is the apocalyptic Zand-i Wahman yasn (also incorrectly known as the Zand-i Vohuman Yasht or Bahman Yasht), which - despite its name - is neither a portion of the Yasna nor an Avestan language Yasht, but a Middle Persian translation and commentary on a now lost Avestan text.
According to Denkard's summary of the Sugdar Nask 15.12-15 (the Sugdar Nask text has been lost and is only preserved as a summary), Peshotanu is one of seven "immortal rulers," residing in "Khandez" (location unknown). This section of the Sudgar Nask serves as the introduction of the Zand-i Wahman yasn, which goes on to foretell various events, including several that had already occurred by the time the translations were made.
As described in the second half of the Zand-i Wahman yasn, Peshotan will serve as "protector of the religion," and at the end of the "eleventh millennium" will bring about a revival of the faith. Peshotanu will live that long because he has gained immortality through his devotion to God.
Until the revival - which will come when the daevas will have exceeded their term of rule by 1,000 years - Peshotanu will live in a fortress in Khandez with 150 of his disciples. Then, Peshotan will come down to battle the armies of the demons and restore Iran and its religion. In the fight, Mihr (Avestan: Mithra) will intervene on Peshotanu's behalf, and together they will drive the demon Kheshm (Avestan: Aeshma) and his forces back into the underworld.