The origins of the Esoteric Order of Dagon is as old as the seas themselves. The cult worships a variety of aquatic deities, Cthulhu, Hydra and most notably Dagon.
Esoteric Order of Dagon was the primary religion in Innsmouth after Captain Obed Marsh returned from the South Seas with the dark religion circa 1838. It quickly took root due to its promises of expensive gold artifacts and fish, which were desired by the primarily-fishing town.
Their most powerful centre of worship was in the sub-continent we now call Atlantis. Centuries of cross-breeding with Deep Ones and Humans have caused a tertiary race of hybrids that outwardly seem Human yet devolve into full Deep Ones once they reach adulthood.
Despite being an aquatic based power they have developed a unique and powerful technology that equally combines with science with sorcery. Like the ancient god Neptune, they also possess a technology that allows them to create earthquakes and tidal waves.
Their relationship with the Migou is questionable but it is known that they have an extreme hatred for Cthonians.