King Proteus was the catalyst in the story of Bellerophon. Bellerophon's journey begins when he is accused of trying to seduce the wife of King Proteus. He is sent into to exile to the land of King Iobates of Lycia. Proteus wanted Lycia to kill Bellerophon, but Iobates feared the wrath of the gods if he murdered a guest. So he sent Bellerophon on a mission that Iobates deemed impossible: to kill the fire-breathing monster the Chimera. An alternate version of the beginning of the quest is that Bellerophon wandered into Proteus, who grew intensely jealous of him. Proteus was the son-in-law of Iobates, King of Lycia, and sent Bellerophon to him with a sealed message that asked to kill Bellerophon. Lycia at the time was in the middle of a horrific plague and Iobates didn't want to strain the population with a war, which would surely be the result if he murdered Bellerophon. Instead, he sent him on an impossible quest: the kill the Chimera.
Proteus is a son of Poseidon or Oceanus and a Naiad. He is sea-god, herdsman of Poseidon's seals, and is able to change his shape and has the gift of prophecy. He will shapechange to avoid having to prophecy; he will only foretell the future to someone who is capable of capturing him. His children include Eido and Theoklymenos with Psamathe, Polygonos and Telegonos (both killed by Hercules), and Eidothea.
There is a story, which says that at one time Aristaeus [?] (son of Apollo) bees all died of a disease and he went to his mother, Cyrene, for help. She told him that Proteus could tell him how prevent another such disaster, but would do so only if compelled. Aristeus had to seize Proteus and hold him, while he changed shape. He did so and Proteus eventually gave up and told him to sacrifice 12 animals to the gods and leave the corpses in the place of sacrifice and return three days later. When Aristaeus returned after the three days he found in one of the carcasses a swarm of bees and they were never again troubled by disease.
From this Proteus comes the adjective protean, which describes traits appropriate for a shapeshifter, such as extreme mutability or versatility.
The Greek writer Homer writes of Proteus in Odyssey 4: 412. According to Homer, the lighthouse island of Pharos situated at Alexandria on the Nile Delta was the home of the oracular Old Man of the Sea and herdsman of Poseidon's sea-beasts. In Greek mythology Proteus was a minor sea-god endowed with the gift of prophecy and his ability to change shape is from whence the word 'protean' is derived and from whence Proteus as 'symbol of the first matter' i.e. the prima materia of alchemy originates.
The German alchemist Heinrich Khunrath (1560-1605) also wrote of the shape-changing sea-god who, because of his relationship to the sea, is both a symbol of the unconscious as well as the perfection of the art. Alluding to the scintilla, the spark from 'the light of nature' and symbol of the anima mundi , Khunrath in Gnostic vein stated-