Dread Cathulo, also known as Dagon, is the god of the sea in the pantheon of DARK•HERITAGE. Not known as a friendly god, it is in fact the goal of sailors and coastal dwellers everywhere to keep this guy asleep. His sleep is a magical sleep; and although he stirs on occasion (causing storms and waves that wreck ships and flood coastal cities) he doesn't truly wake, and is believed, in fact, to be not only asleep but bound beneath the sea in his submerged prison-city of Rillyè.
The mythology also states that Cathulo was once awake completely, and rampaged throughout the seas and coastal areas, and even far onto land, in the time before the rise of human civilization. There, it came across another titanic being, Ubbo-Sathla, and the two of them waged terrible war across the landscape, scarring and deforming it in ways that are still visible today, uncountable eons later. The spawn of Ubbo-Sathla, including the vile shoggoths, and the spawn of dread Cathulo warred alongside their sires, and the instinctual animosity of that ancient conflict still drives these creatures, who today are in many ways nearly mindless. Both beings now slumber, some say recovering from the wounds they received in this titanic struggle--Ubbo-Sathla in the depths of the earth, and dread Cathulo under the sea.
In the DARK•HERITAGE setting, it is much more likely that the common man will propitiate rather than worship the gods. It is best to divert their attention rather than call it. To this end, most rites involving Cathulo are about keeping him asleep. When praying for good weather for a voyage or during hurricane season, wine or other liquor is poured into the sea (or harbor) in an effort to ensure that Cathulo remains asleep.
Cathulo is the name of this god in Terrasan, but he has other names as well. The Qazmiri know him as Dagon. They do not believe, as do the Terrasans, that Rillyè is located in the Mezzovian Sea; rather they believe it to be in the open ocean, far from the shores of Terrasa. They also have rumors of nations destroyed by Dagon in times gone by, similar to the story of Arggo. Also, they have a strange tale of one Obed al-Marssa, a man who discovered a muck-covered new land which rose spontaneously from the depths of the sea. Obed later settled in a coastal town, and brought worship of Dagon to its people. They had a bounteous harvest from the sea as a result of their worship, but horrible things happened in the mystery cult, including coupling with inhuman creatures of the sea--debased and diminished spawn of Dagon himself. The progeny of these unholy couplings would appear human--at first--but eventually their heritage would out itself, and they began a blasphemous transformation into inhuman Deep Ones, creatures of the sea.
Rumors of this cult of Dagon are still common among the Qazmiri, although seldom is any far-flung town actually openly accused of such heresy. The myth of Dagon's cult has spread to Terrasan territory as well, where Dagon and Cathulo were naturally enough conflated, if in fact they weren't already the same being from the get-go.
As Dagon, he is often depicted as a bearded and crowned man with a fish's tail. This representation has spread to Terrasa as well. But in benighted and forbidden texts, such as Prophecies of the Daemon-sultan, The Book of the Black Prince, The Book of Eibon, The Eltdown Shards, and others, he is described as a monstrous creature of the sea, with razor-sharp teeth as found only on bizarre and hideous deep-sea fish like dragonfish or anglers, clawed hands, an only vaguely anthropomorphic body and head, a long tail, and many, writhing tentacles. He has a few other names, in the local languages--Ketos in the ancient Terrasan, Kraken in balshatoi, and even Leviathan in the vernacular of many areas.