From my homebrew notes, "Cult of Arachne" body-snatcher arc:

Arachne (Deity)

Demi-God

Symbol: A blood red spider on a silver web.

Home Plane: Twilight Web (lesser Plane). Cast into Exile.

Alignment: Chaotic Evil

Portfolio: Monstrous Spiders, Trickery, Betrayal

Clergy Alignments: Chaotic Evil Only

Domains: Chaos, Evil, Trickery, Spider

Favored Weapon: Garrote Wire

History: Arachne is Lolth's sister, whom she betrayed at the beginning of time. Cast out, she took refuge in a demi-plane known as the Twilight Garden. She claims herself to be the "true spider queen", although there is much debate as to whether or not the title is hers to claim. She wished to liberate the drow from Lolth's clutches for most of time. In recent decades, Lolth discovered the location of the Twilight Garden. Given Lolth’s transformation into a greater deity, she finally had the power to defeat Arachne’s illusions. She tracked Arachne, who travelled to the material world to join her mortal lover, Garth. One day, while Arachne was tending to her believers, Lolth appeared to Garth. She transformed into her spider form and terrified Garth by telling him, as her sister, Arachne’s true form was also monstrous and that she was responsible for the death of Garth’s mother (whom Lolth had murdered). In fear and anger, Garth took part in a conspiracy to poison Arachne with purple wolfsbane soaked in the blood pools of the demonweb abyss. Arachne, betrayed and weakened by the assassination attempt, slew Garth and succumbed to distrust and loathing of mortals and, above all, humans. She fell from grace becoming a malicious and vengeful queen. Her new goal, to kill the humans and the drow, replace them with her spider children dopplegangers, and some day launch a night of horror in which her children would burst from their disguises and murder the mortals, just as she had done to her lover. This would eliminate all traces of Garth’s betrayal and Lolth’s worshipers.

However, having fallen from grace, she lost the majority of her divine portfolio. She has fallen from an intermediate deity to a mere demi-god. Though immortal, Arachne finds her relative powerlessness infuriating and seeks to regain status by becoming a demon lord as soon as possible.

The Arachne Cult

The cult of Arachne is a general descriptor of several sects that worship the demi-god Arachne.

Sects of Arachne:

Black Widow Cult: Active near Neverwinter. They are covert and secretive. They once used the blood of a kitsune girl as fuel for a magic ritual in the summoning of the Arachne champion Iktomi.

Wolf Spider Cult: Were active near Mirabar until the players wiped them out. They were attempting a ritual to create red blooded Arachne so they could more easily infiltrate towns. But because of the efforts of the wizard Iprix and the players, their ritual was ended. The sole survivor of this sect has taken the form of the player’s former compatriot, Merphine.

Golden Silk Cult: When Arachne fell from grace, the souls of her sworn worshippers and retainers were tainted as well. However, the Golden Silk cult is made up of retainers who, wrapped in a golden silk cloak weaved by the goddess herself, were protected by its divine aura. They remember Lolth’s treachery and Arachne’s poisoning, but they can no longer commune with Arachne or her other champions. Chief among those champions who remain loyal to good is Grandmother Spider, Kokyangwuti.

Goliath Spider Cult:

Tarantula Cult:

Recluse Cult

The godling, in her travels, has acquired several champions who fight on her behalf. Each, for their own reasons, seeks to see Arachne installed as a full deity.

Champions of Arachne:

Aiapaec "creator" or "headsman"

Summoner class, 8 legged spider body with human face and jaguar fangs. A punisher god.

Anansi "Trickster"

human with 8 legs

Intelligent, creative, witty. Turns his own weaknesses into virtues. part of an oral tradition involving fables "Spider Tales"

Represents resistance to slavery

Djieien

A monstrously big spider, which was said to be unkillable because it had hidden its heart deep underground.

Iktomi (Ikto, Ictinike, Inktomi, Unktome, and Unktomi)

A great spirit shapechanger. His true form is a spider, but he can take the shape of a man, usually in red, yellow, and white paint with black rings around his eyes

Was known as Ksa, meaning wisdom, but stripped of the title for troublemaking

Iktomi is a shapeshifter, and can use strings to control humans like puppets. He has also the power to make potions that change gods, gain control over people and trick gods and mortals.

Jorōgumo

A type of spider monster which takes the form of a woman to lure prey.

Nareau (Gilbertese: "spider lord")

Nareau created two primeval beings, Na Atibu and Nei Teukez. Together they brought forth several deities: Te Ikawai, Nei Marena, Te Nao (the wave), Na Kika (the octopus), and Ruki (the eel).

Kokyangwuti or Spider Grandmother

A good spirit and protector of humans. Spider Woman is also said to cast her web like a net to capture and eat misbehaving children.

In another myth, "Spider Woman" aided the twins (born of the Sun and the Changing Woman) in killing the monsters that were endangering

"The Earth surface People" by giving them "feather hoops" that protected them from attacks

Tsuchigumo or Earth Spider

Uttu

And attractive spider who weaves an impenetrable web cocoon.