Dagon

Dagon is a demon lord, also called Prince of the Depths. His realm is the 89th layer of the Abyss, and is known as Shadowsea. Dagon is an obyrith.

Dagon is first mentioned in the first edition Dungeons &amp; Dragons sourcebook Monster Manual II, where it is said in passing that he rules a liquid layer dominated by marine dretches, hezrous, krakens, and horrible fish-monsters.

Description
Dagon's form is a mixture of both octopus and fish. Dagon sprouts countless tentacles and is covered in black, rubbery skin that is punctuated with many red, unblinking eyes. Fish scales shield his flesh, and row upon row of long fangs jut from his maw. He stands more than 40 feet tall and is considered one of the most fearsome of the demon lords.

History
Dagon's history in the Realms lies below the surface of the Sea of Fallen Stars and in the waters west of Maztica. Dagon and his minions lurked for a long time in the Trench of Lopok and were only known as "Those Who sleep Below". They infested the dreams of those who swam in the Sea of Fallen Stars with nightmares. The most ambitious of the demons was Prince Dagon, who planned to overcome a pantheon of sea creatures and achieve their divine powers. To reach this goal, he brought the depths of the Sea of Fallen Stars under the control of his servants and their forces. The next step was made with long forgotten eldritch magic. He restricted the influence of the deities of the Shalarin in the Sea of Corynactis, on the West of Maztica.

The next step was the creation of five "wild tides" to sweep large numbers of sharlarin into the Sea of Fallen Stars, where his minions could slaughter them. The first wild tide began in -1509 DR with opening of the Wildtide Portals connecting the two ocean realms. Many Shalarin were swept into the Sea of Fallen Stars where roughly 70% died under the attacks of Dagon's servants. The rest was only rescued by the intervention of Dagon's enemies, like merfolk.

Dagon repeated this tactic every 720 years and the last wild tide was in 1371 DR. This time the portal stayed and became permanent. The shalarin of Faerûn kept the portal a secret, fearing that others could use it for their own ends. But another fact was more disturbing for them. Between the fourth and fifth tide, the shalarin of their homelands near Maztica, all but abandoned their gods because they've grown silent. Instead of the gods, they began to venerate the demon Dagon and his cult became the dominant religion in the Sea of Corynactis. The shalarin of the Sea of Fallen Stars cut of the travel between their communities. But it was too late and the cult of Dagon had already taken root among their ranks or grown in secret.

Dagon also seems to have heroic "good" progeny in Faerûn, one for certain in the form of Captain Thoster, one of the heroes attempting to stop the eladrin Malyanna from opening the Far Manifold with the Key of Stars. Captain Thoster is a "merchant" (pirate) with a macabre sense of humor and a loyal friend. Thoster's heritage manifests itself in increments periodically during this quest; originally he believes it to be of Kuo-Toa origin. Eventually, it's revealed to him (in an extremely painful transformation) that he is in actuality a Demon Scion, a direct descendent of Dagon.

Cult of Dagon
Dagon is served by aquatic demons, especially wastrilith, and is worshipped by aquatic races such as kraken, chuuls, sea hags, water nagas, and kuo-toa.

The Outcast Dagon
The demon lord Dagon should not be confused with the exiled devil of the same name, who dwells on Avernus, first layer of Baator. Originally known as Jaqon, Asmodeus forcibly changed Jaqon's name to Dagon to thwart attempts to summon the offender.