The cult of Gison Thorelon is the most despicable organization known to all free people.
While no one disputes the existence of the being known as Gison, his true nature is clouded in mystery. It is this very uncertainty that allows his cult to prosper, spreading their message of fear and death. What little is known seems to imply that Gison is, if not immortal, at least extremely long-lived. Some suggested that he might belong to the race of the kerense, from which came the dragon-lords, but this does not seem likely because of his portrayal elsewhere.
In artwork, Gison is always depicted as a humanoid being, but with a cyclopean aspect. Other than these two standards, nothing else is consistent. He is at times portrayed as average size and at times gigantic (which seems unlikely given his underground status). Even his singular eye is depicted in various styles and designs. Some depict him clad in red and black robes and cape, while others show him without clothing or accoutrements of any kind.
Gison’s worshippers proclaim him to be the Lord of the Underworld, a blatant falsehood. However, it has been spread so far and wide that far too many otherwise enlightened people have fallen prey to this lie. Gison is said to collect the souls of the sinful… or those lost in battle… or those sacrificed in his name… The sects vary on this point. In any event, the mere invocation of his name is enough to inspire a sense of dread in the average citizen.
In one probably apocryphal legend of Kinon the Young, the hero of many tales was said to have encountered Gison in a cave beneath the mountains of Yi. In the story, Gison is surrounded by an honor guard of dark warriors and demons. When one of Kinon’s companions is mortally wounded by one of these demons, Kinon challenges Gison to a duel of wits over his friend’s soul, which Gison seems about to claim. Kinon is ultimately successful; he and his companions are allowed to leave Gison’s realm. (The story seems unlikely since Kinon is never recorded as having traveled to that region anywhere else, and the odds of one man having encountered as many creatures and beings of legend as Kinon are too ridiculous to be taken seriously.)
It is not worthwhile to describe the horrific ceremonies conducted by the Gison cults, except that they almost always involve human sacrifice. These vile gatherings should be vehemently opposed by all true servants of the Eternal, wherever they may be found.
-from the memoirs of Machaira Ktistes, elven smith