Pegasus is one of the best known mythological creatures in Greek mythology, brother of Chrysaor, born at a single birthing when his mother was decapitated by Perseus. He is a winged divine stallion usually depicted as pure white in color. Pegasus was sired by Poseidon, in his role as horse-god, and foaled by the Gorgon Medusa. Greco-Roman poets write about his ascent to heaven after his birth and his obeisance to Zeus, king of the gods, who instructed him to bring lightning and thunder from Olympus. He was captured by the Greek hero Bellerophon near the fountain Peirene with the help of Athena and Poseidon, hallows the hero to ride him to defeat a monster, the Chimera, before realizing many other exploits. His rider, however, falls off his back trying to reach Mount Olympus. Zeus transformed him into the constellation Pegasus and placed him up in the sky.