You have to go back a long time, when in a time of thaw in the Granada mountains, a shepherd was feeding his cattle near a lagoon. While the animals grazed, the man rested under a tree, enjoying the landscape and the peace of the mountains.
There was a moment when his calm was disturbed when he heard a voice, but it wasn't just any voice. Those words seemed to come from a diabolical entity, which cried out to be released from its captivity, wherever it was locked up. And it was not the only thing that was heard: a second voice replied that because of his wickedness he still had to remain locked up for some more time.
Immediately afterwards, two men appeared, dressed in the robes of magicians, and threw a net into the lagoon while crying out strange prayers. They pulled a white mare out of the water, but they did not seem satisfied with the result. They threw the net again, this time capturing a beautiful blue mare, but this time they were not satisfied either. When making a third attempt, the color of the animal that came out of the lagoon was black. The two supposed magicians, indignant, picked up their net and left the place, leaving the disoriented mares there.
Before the disoriented pastor could get out of his astonishment, something happened again that left him stunned. A very loud whistle, coming from the depths of that lagoon, made the mares enter the waters, returning to the place where they belonged.
Tradition says that the magicians were looking for a red horse that was hiding in the lagoon. Whoever possesses it will have absolute power. But of course, instead of that, they had taken three mares of different colors outside that were of no use. So they had to put off the search for a year, because you can only cast the net three times after each thaw.