There was once a time when the Valley of Jauja, where the Mantaro River now flows, was covered by the waters of an enormous lake. In the middle of this lake there lived a serpent.
At first the serpent was all alone. But in time the rainbow created a second serpent to keep the first one company. It was not quite so large and also considerably darker than the first, which, when fully grown, was of a whitish color. But the two became enemies and soon were fighting for control of the lake.
Their struggles were violent, and often the lake would be stirred into great columns of water, upon which the larger serpent would rise far into the sky. Once, as it swooped down upon the smaller one, it attacked with such fury that it lost a huge piece of its tail.
Angered by these disturbances, the god Ticsi sent a thunderstorm. It struck both serpents dead by lightning. As they sank back into the swollen lake, it broke free at its southern rim and all the water came pouring out.
When the valley had been formed in this manner, then the first two human beings, called Mama and Taita, were hurled forth from a spring. Until then they had remained hidden in the earth for fear of the serpents. In later days, the descendants of this pair constructed the temple of Huarivilca, the ruins of which can still be seen.
Today it is widely believed that the serpents still live in a cave where from time to time they grow to an enormous size. Taking advantage of the winds that blow up during thunderstorms, they try to ride into the sky. But they are always killed by lightning striking down through the clouds.
When a serpent appears in the sky, if it is white, the year will be good; if it is black, the year will be bad.