Poseidon was an interloper deity of waters in some forgotten age of history, for like the sea, he was fickle in nature.
 
Poseidon now resides in the Dreamlands, in the Ulthar, the City of Cats, where he maintains the cemetery and a cliffside cottage. He is happy here, despite rarely leaving the cemetery grounds. Often have dreamers found themselves in Ulthar, lost or confused, drawn to Poseidon's guiding light. 
 
Poseidon had some small part to play as guide and mentor to Liona Lyonn, one of, if no the, most powerful dreamer to have ever dreamed.