Many monsters of Greek Mythology are descended from one major source: Echinda, the mother of monsters. A great number of Greek monsters are directly associated with the sea, and sea dieties. Many of Poseidons's offspring were monstrous in appearance. Gods created monsters themselves on numerous occasions. Not only were monsters born from gods, but gods transformed people or other things into various hideous beasts. Many times a god is scorned only to take revenge on the mortal by turning him or her into a disgusting monster. There are many circumstances that can lead to this metamorphosis, but three specific cases are very likely. One case is when an immortal has been romantically involved with a mortal and his or her spouse or lover finds out. The spurned lover takes revenge on the unsuspecting mortal by changing him or her into a monstrous entity. A second case is when a god is turned down by an immortal, and takes revenge upon the human by morphing him or her into a terrifying monstrosity. A third case, appearing less often than the other two (at least with more well known Greek monsters), is when a mortal defeats a god or challenges his or her authority. The god teaches the mortal a lesson in humility by changing his or her for the worse. For the most part though, sea progeny exhibited grotesque and appaling elements leading to their being classified as monsters. The sea of monsters started when Ge mated with Pontus and produced Phorcys and Ceto, who in turn mated and produced the Gorgons, the snake-like mosters with serpents for hair who turned those unfortunate enough to gaze upon them into stone. Phorcys and Ceto also bore Ladon (a dragon) who was protector of a tree of golden fruit. Medusa (one of the gorgons, who was killed by Perseus) mated with Poseidon to produce Chrysaor, who mated with an Oceanid (Callirhoe) to produce the monstrous offspring Geryon and Echidna. Echidna mated with Typhon and had Orthus (the hound of Geryon), Cerberus (the hound of Hades), the Lernaean Hydra, and the Chimaera. Echinda also mated with Orthus and had the Theban Sphinx and Nemean Lion. These monsters play a major role in increasing the power of the legends of various greek heroes.