The Esoteric Order of Dagon was established in 1833, 13 years after the official Founding of the City of Malton. While the exact circumstances to the founding of the Order remain a mystery to this day, it is known that there has always been a Grandmaster of the Order since it's inception. Acting as the voice and will of the Order, the Grandmasters had led the Esoteric Order to preeminence in Arkham until 1912, when intervention from the government due to riots caused by the Order led to what is now known as the Great Fire of Malton. Surviving rioters and dissidents were rounded up and the Order was forcibly disbanded, with a few members managing to avoid capture and flee Malton. The Esoteric Order had met a sudden and fiery end.
Though there have been multiple attempts to re-establish the Order in the years following it's destruction, the Outbreak and Quarantine is what finally enabled the Order to once more come into power- openly converting survivors to a common cause without fear of government reprisal. Before the initial outbreak, a member of a secretive group called the Silver Twilight Lodge managed to locate a number of murals and tablets containing writings of an ancient language. Through them, the members of the Lodge were able to learn the Word of Father Dagon in its entirety as it was known to those below in Y'ha-nthlei. Forewarned of the coming outbreak in Malton, the Silver Twilight Lodge, now known as the Reformed Esoteric Order of Dagon, was able to stockpile resources and ride out the zombie apocalypse in an underground shelter.
A decade has passed since Malton was quarantined. Emerging from their place of refuge, the Order sets out, armed with the knowledge of the Divine Purpose, once more seeking ascension.
The Order currently reside in Arkham, wandering around nearby suburbs to enlighten the masses. Members of the Order have been seen gathering in Miller Library, where they're known to peruse the various esoteric texts to better understand the teachings of the Grandmaster. The Elder Alley is another known gathering point, with members seen chanting and conducting various eldritch rituals.