In Greek mythology , the prophetic old man of the sea and the shepherd of sea animals such as seals.
He was subject to Poseidon . He knew all things
past, present, and future
but disliked telling what he knew. Those who wanted information from him had to catch him sleeping and bind him. He would try to escape by changing his form, but if a captor held him fast he gave the wished-for answer and plunged into the sea.