The Mongols had an almost religious veneration for one of their favorite drinks, the "kumiss" made from fermented mare's milk. At the same time, the Great Khan himself, when he built the famed city of Shangdu (Xanadu), had a herd of sacred white mares, whose milk only Kublai Khan could consume. As noted in the history of Shangdu,

The Mongols were a hunting race, and the Great Khan’s imperial hunt was not forgotten in designing Shangdu. To the north and west of the outer city walls was a game preserve, carefully landscaped in this seething sea of grass to provide meadows, woods, coppices of trees, and lakes. It was stocked with game, mostly varieties of deer, and dotted with fountains and streams. ..The park itself was also surrounded by an earth wall, and apparently the Khan’s sacred white mares – who provided milk which only the Great Khan could drink – were also raised here. "

Horses were utterly essential to the Mongol way of life, and the White Mare not only symbolized perfect beauty but perfect utility . . . thus, the Khan's herd symbolized the fertility and nurture to be found in the wild, harsh lands of the steppes.

As for Mongol folk tales, they are (not surprisingly) full of violence, magic, and striving. Our own 'take' on the White Mare legend owes much to one of the best online sources for Mongol folk tales (including the near-magic horses of the steppes), and there are many other introductions to the magical, dangerous world of Mongol folklore.

A Journey in Southern Siberia: Varhan Tulai Habun

BBC: Mongol Folk Tales

How Storytelling Began Among the Mongols

Traditions, Values and Beliefs