Tishtrya
Also known as: Tishtar, Tir, Sirius

Mythological Narrative
The star Sirius as a rain-bringing yazata, who in the Tir Yasht descends to the cosmic sea as a white horse, is at first overcome by the black horse of the drought demon Apaosha, and then, strengthened by worship, defeats him and releases the rains.
Scholarly Commentary & Evolution
## The Tir Yasht
Yasht 8 is devoted to Tishtrya, the brightest star in the sky. He flies toward the sea Vouru-Kasha as swiftly as the arrow that the archer Erekhsha shot from Mount Khshaotha to Mount Hvanvant, and Ahura Mazda, the waters, and the plants aid him, while Mithra opens a wide way for him. He takes three forms in turn: a young man of fifteen, a bull with golden horns, and a white horse with golden ears.
## Battle with drought
As a white horse he goes down to the sea, where the demon of drought, Apaosha, rushes to meet him as a black horse 'stamped with brands of terror'. They fight hoof against hoof for three days and nights, and Apaosha wins, driving Tishtrya from the sea. Tishtrya laments that men do not worship him with a sacrifice in which he is invoked by his own name; when he receives such worship, he returns with renewed strength, defeats Apaosha at noon, and the waters of Vouru-Kasha rise in clouds that carry rain to the seven regions of the earth.
## Festival and later tradition
The summer festival of Tirgan, on the day Tir of the month Tir, honored Tishtrya and was later linked with the legend of the archer Arash (Avestan Erekhsha), whose arrow fixed the frontier between Iran and Turan. Tirgan is still celebrated in parts of Iran, with water-splashing and the tying of colored bands.
Academic Discussion & Critique
Exchange peer-reviewed hypotheses, comparative Indo-European etymologies, and archaeological field interpretations regarding Tishtrya.
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