Glaucus was a Greek sea god. He was originally a mortal fisherman, but turned immortal upon eating a magical herb. He had the gift of prophecy and often rescued fishermen sailors, having previously been one.
Originally a fisherman from Anthedon in Boeotia, Glaucus accidentally discovered a herb that brought fish back to life and deciding to taste it himself. He was inadvertently turned into a merman-like being and was thus forced to forever dwell in the ocean.
He was welcomed by Oceanus and Tethys, who taught him the gift of prophecy. Glaucus later settled near the island of Delos, prophesying to those who requested it. He later taught the art of prophecy to Apollo, who was born on Delos.
Circe and Scylla
Glaucus is well-known for his love for Scylla, a beautiful nymph and the daughter of Phorcys and Ceto. Scylla, for her part, was repulsed by his fish-like features and fled onto land to escape him. Thus Glaucus approached Circe for a potion to help him. Instead, Circe herself fell in love with him. She tried to convince him to abandon Scylla for her, but he replied that trees would grow on the ocean floor and seaweed would grow on the highest mountain before he would scorn Scylla. Thus Circe poisoned a pool in which Scylla bathed, turning her into a monster with six dogs sprouting from her waist.