The Night Shade of Greyhawk and the Hallowed Revenant Amphoras
Light must be snuffed, perfection decayed, order dissolved,
and minds fragmented.
Tharizdun was described in Dragon #294 as a pitch-black, roiling, amorphous form. As the Dark God, he is described as an incorporeal wraithform, black and faceless.
Tharizdun has been depicted on the cover of Gary Gygax's Gord the Rogue novel Come Endless Darkness as a huge, bald, humanoid man, with claws, greenish-black skin, and pointed ears.
Tharizdun is sometimes worshipped as an entity called the Elder Elemental Eye (a being similar to Ghaunadaur), but few of these worshippers recognize the two as being the same entity. The Elder Elemental Eye is described as a huge, mottled, tentacled being, or as a pillar of vast elemental force with a body of burning magma, radiating steam.
It is believed that Tharizdun has no allies, given his desire to destroy the entire universe. Should he ever escape from his prison, it is thought that even the most evil of deities work with their good counterparts to return Tharizdun to his prison. However, the Dark God has been known to work his will secretly by employing various demons (with or without their knowledge) to do his bidding. Examples of fiends so used include Iuz and Zuggtmoy, and the Princes of Elemental Evil.
On Oerth, Tharizdun is particularly opposed by Pelor and Boccob.
The Demiplane of Imprisonment is hidden somewhere in the depths of the Ethereal Plane, resembling a swollen, crystalline cyst nearly a mile in diameter. The ethereal substance surrounding the demiplane boils with the dreamscapes of Tharizdun's worshipers and others whose dreams the dark god invades.
Tharizdun's doctrine is to destroy all and everything encountered (himself included), as he puts it:
The very threads of existence must be torn asunder, then burned, then the ashes scattered, until all is nothing and no one exists to remember existence.
Most of Tharizdun's ancient scriptures are long lost. The only one known to remain is the Lament for Lost Tharizdun, penned his "last cleric," Wongas.
Tharizdun's worshippers are often insane. Their ultimate goal is to free their dark deity from his prison. He is rumored to be worshipped by the Scarlet Brotherhood, though these followers are actually a splinter sect of the organization known as the Black Brotherhood or The Blackthorn.
Like his lay worshippers, many of Tharizdun's priests are mad. Those who are not mad believe (mistakenly) that they will reap great rewards and privileges for their aid in freeing him. All of his clerics are extremely secretive and trust only fellow cultists. They lead foul rituals, including human sacrifice, and search ancient sites for clues to freeing their deity. Due to Tharizdun's imprisonment, his priests must remain in contact with a site or object holding some of the Dark God's power in order to use their magic. Their favored weapon is the "spiral of decay," a bizarre weapon about which little is known. Those priests who follow Tharizdun's Elder Elemental Eye aspect have used a weapon known as a "tentacle rod" (a rod topped with animate tentacles), but it is unknown if this is the same object.
Tharizdun's temples (often in the shape of black ziggurats) are usually hidden, due to necessity. Known places of worship include an ancient temple located in the Yatil Mountains, as well as a more recently-discovered temple in the Lortmils, near the Kron Hills. Although not many people in the Flanaess are aware that Tharizdun exists, it is said that public knowledge of one of his ziggurats would be enough to "raise an army of paladins"
Tharizdun has many known artifacts. "One" that is known is actually many: a collection of gems known as the 333 Gems of Tharizdun. Their current location is unknown, but it is certain that the collection was split up long ago. Other artifacts associated with Tharizdun include the sword Druniazth and the Spear of Sorrow. The Scorpion Crown was gifted by him to the last king of Sulm. Still another artifact, the Weeping Hexagram, is in the hands of the Scarlet Brotherhood.
Some say that Tharizdun originated in the Far Realm or in a previous universe. Tharizdun was imprisoned eons ago by the forebears of those beings known as the Great Powers, although it is said that Pelor was also involved. It's said that both good and evil deities worked together to ensure his imprisonment. As the Dark God, he is credited with the corruption of the Seelie Court. Through the Scorpion Crown, he is said to have destroyed the ancient kingdom of Sulm.
He was imprisoned long ago, but his prison may weaken at times, allowing his influence to creep out into the worlds beyond. Tharizdun's temple in the Yatils is thought to have been originally defeated with the aid of the legendary Six from Shadow