Originally, Ghaunadaur was a member of the drow pantheon but following the War of the Spider Queen he left the pantheon to break off on his own. He is also known as That Which Lurks and The Elder Eye. His portfolio includes slimey creatures, outcasts and rebels.
Ghaunadaur is an unpredictable deity. False worshipers may be rewarded by it, sometimes even with permanent magical boons, but they might just as well be devoured by The Elder Eye without a second thought. Ghaunadaur enjoys watching large horrible monsters as they hunt and devour their prey, causing much suffering. When Ghaunadaur leaves the Inner Planes he is always silent, but some old records mention a gibbering and bestial language being spoken in the god's court. When communicating it uses telepathy and keeps its conversations blunt and simple.
Ghaunadaur is a very ancient deity, rumored to have emerged from the primordial ooze itself. In that age it was worshipped by the largest of slimes and other crawling creatures, many of which contained an alien intelligence. In a fit of fury for an unknown transgression, Ghaunadaur struck most of them mad and took their intellects. As an unforeseen result, many of these worshipers ceased to exist, which caused The Elder Eye's power to collapse. Only in recent millennia have some evil beings turned back to Ghaunadaur, looking for an alternative to the established deities. Ghaunadaur is only a member of the drow pantheon because of the worship of drow that became disaffected with Lolth.
The church of Ghaunadaur consists of cults scattered throughout the Underdark, each dominated by a single individual. There are only a few drow and aboleth cities that served as exceptions, with a more organized clergy. Ghaunadaur also has an aspect in the tanar'ri lord Juiblex and enjoys the worship of that guise's demonic cults. Clerics of Ghaunadaur are required to serve the Elder Eye completely and do whatever pleased it most. The main duty of Ghaundaur's clerics is to ensure, in any way necessary, that Ghaunadaur's altars were supplied with a steady supply of sacrifices. Clerics successful in these sacrifices are rewarded with magic power and items. Ghaunadaur enjoys (most of all) those creatures that willingly offered themselves to it, whether or not they had been charmed or coerced by its clerics. Those clerics that succeed in bringing willing sacrifices to Ghaunadaur's altars are its most favored and highest ranked servants.
Ghaunadaur encourages its clerics to familiarize themselves with using and creating acids, poisons and alchemist's fire. Many clerics also take training as fighters or enchanters. Ghaunadaur doesn't care much about the bonds that hold its clergy together, and in accordance with his doctrine, clerics that murder each other to attain higher status don't displease the Ancient Eye.
VestmentsPriests of Ghaunadaur must wear clothing of hues pleasing to the Elder Eye. Typical raiment includes a full-length robe with voluminous sleeves, a dark tabard emblazoned with the symbol of the Elder Eye, and a gleaming, silver skull cap. All priests wear their hair long and unbound, but beards and mustaches are not permitted. The holy symbol of the faith is a sphere of black obsidian at least 3 inches in diameter, which is sometimes worn on a chain around the neck. Such spheres are often eveloped in a nimbus of mauve-hued continual faerie fire.
When adventuring, Ghaunadaur's clergy employ whatever weapons, armor, or equipment is most appropriate to the task at hand. Most priests are careful to always wear hues pleasing to the Elder Eye, however, just in case it is observing their performance, even going so far as to tint their armor and weapons.
Temples & ShrinesShrines and temples devoted to Ghaunadaur are foul rooms, often filled with fetid mists and fetid smelling slime trickled down the walls. These manifestations are strongest around the halls where sacrificial rituals take place. The stench is so strong that others would perceive it as swimming through rotten sewage.
RitualsGhaunadaur's clergy prayed for their spells once per day at any time the local cult deemed important. The Elder Eye expected each prayer to be coupled with a sacrifice. It preferred living offerings, but when that was impossible it also accepted bones and food which were burned in oil while braziers of perfumed incense were burned as well. If the worshiper could not deliver any offerings to the deity, they were required to perform their prayer while holding one unprotected hand in an open flame.
Ghaunadans would go on the Gathering, which consisted of incursions meant to kidnap and abduct sentient beings that would be destined to the sacrificial altar of Ghaunadaur. These individuals would be drugged and held under compulsion, pushing them to walk up to the altar, where the leading cleric would pray and turn into slime. The slime would envelop the victim and consume it. This process could be repeated several times depending on the number of available subjects.
The prayers and rituals the Ghaunadans directed to the Lord of Slime were as ill-defined and amorphous as their god. Each cleric manifested prayers in the manner they saw fit and no cleric would suspect a worshiper of treachery or blasphemy for uttering nonsense or unintelligible gibberish.
All creatures have their place, and all are fit to wield power. Those who hunt weed out the weak and strengthen the stock of all. Those who rebel or who walk apart find new ways and try new things and do most to advance their races. Creatures of power best house the energy of life, which Ghaunadaur reveres and represents. Make sacrifices to the Eye, persuade others to sacrifice themselves to Ghaunadaur or in service of the Eye, further knowledge and fear of Ghaunadaur, and in the end give yourself to Ghaunadaur in unresisting self-sacrifice. Convert all beings to the worship of Ghaunadaur. Slay all clergy of other faiths, plundering their temples and holdings for wealth to better your own lot and to further the worship of Ghaunadaur.
Ghaunadaur frequently manifests to aid priests or worshipers as a reddish-purple giant slug, but at will it can alter its form into an amorphous free-flowing shape like a jelly, rear up into a giant roper with up to 10 long purple tentacles, or appear as a sticky green substance that emerges from the ground.
He can also appear as a roiling purple cloud 4 to 6 feet across. From the center of this cloud comes a 12" diameter gold eye that opens its lids to bathe the favored creature in a fiery orange light. The light gradually fades to deep red, then a dark purple.
Ghaunadaur occasionally acts through the appearance or presence of alkiliths, darktentacles, deadly puddings, gelatinous cubes, giant ropers (also known as ghauropers), gibbering mouthers, ghaunadan, jellies, oozes, metalmasters, mephits (ooze), ropers, slimes, slithering trackers, slithermorphs, slugs, and storopers.
As a complete loner, Ghaunadaur did not possess a single ally. He directly opposed just about every other deity with a presence in the Underdark. His other major enemies were Malar and the Seldarine. Although an occasional ally of Lolth (whom she tried to use as a simple tool to be thrown away afterward during the War of the Spider Queen) when her inevitable betrayal came, he demonstrated power unseen since before his fury and left the Demonweb.
It was possible that there was a relationship of some kind with The Patient One and Tharizdun, similar deities of other worlds.