Much of the Underdark is ensnared in the figurative web of Lolth, god of spiders. Lolth considers herself the true god of drow, though other members of the drow pantheon disagree. Lolth is a cruel god who encourages her followers to backstab and betray each other, reveling in their treachery.
Lolth was once known as Araushnee, spouse of the elven deity Corellon Larethian. After attempting to overthrow Corellon with an army of spirits, Araushnee was banished to the Abyss. There, she fashioned an arachnid form for herself and took her current name. Spiders of all kinds are seen as omens of Lolth, especially in the Underdark. Lolth often sends Yochlols, her signature demons, as messengers or spies.
Lolth's worship has an iron grip on the social structure of many drow cities in the Underdark. Recently folk unassociated with the Underdark have heard the spider god's call, guided by trails of spiders to join aboveground cults dedicated to Lolth. Disciples of Lolth proudly wear web-patterned clothing and practice blood sacrifice, preferring unwilling creatures. Their doctrine teaches them to find and kill non-worshipers. Lolth's followers aren't permitted to pray to other gods apart from Kiaransalee and Selvetarm, Lolth's two allies in the drow pantheon.
The stone walls of Lolth's grandest temples are adorned with floor-to-ceiling bas-reliefs of webbing. As a reflection of the matriarchy of spiders, Lolth's faith permits only women to rise to the priesthood. In the Underdark, drow priests of Lolth rule the noble houses of drow cities like Menzoberranzan, where they wield absolute power. Some of these cities' residents despise the tyranny of Lolth's organization, fleeing to the surface or to drow communities that serve more lenient gods of the drow pantheon.
When one of Lolth's worshipers shows great promise, Lolth summons them to the Demonweb Pits for a test of faith and strength. Those who fail the test are transformed into Driders, but those who succeed become Yor'thae, Chosen of Lolth. Yor'thae exercise divine mastery over spiders and carry out Lolth's machinations.
Silken Stewards
Certain disciples of Lolth don't always kill their victims, instead putting them to sleep with Lolth's Sting (see chapter 3 of the Dungeon Master's Guide). The victim awakes cocooned in sticky webs, suspended from the ceiling of a dark temple or underground room. In a matter of hours, a swarm of tiny creatures begins to wriggle in the victim's chest. The last feeling the victim experiences is a hair-raising, tickling sensation that quickly turns to agony as baby spiders chew their way out of the ribcage, killing the host.
Lolth's worshipers who practice this method of spider-egg incubation call themselves the Silken Stewards. The practice was pioneered by House Auvryndar, one of Menzoberranzan's ruling noble houses. The drow of this house found that implanting spider eggs into Humanoid hosts and performing a ritual to Lolth over the body caused the eggs to hatch in mere hours, rather than weeks. A Lesser Restoration spell cast on the host kills the spider eggs, ending the threat.
Silken Stewards provide other disciples of Lolth with a steady supply of spiders used as mounts, trackers, sentries, and front-line forces in service to the Spider Queen. The Stewards raise all sorts of arachnids: Spiders, Giant Spiders, and even Phase Spiders. Silken Stewards wear gloves made of the finest spider silk, and their clothes bear brooches depicting the stylized image of a curled-up spider inside a white spider egg. High-ranking members oversee the implantation of eggs and the accompanying rituals. Middle-ranking members capture Humanoids to use as hosts. Lesser-ranking members rear the hatched spiders and train them.
Followers of Eilistraee are among the Stewards' greatest foes, particularly Eilistraee's militant orders. They lead raids into the Stewards' hatcheries, killing spiders, freeing captives, and curing infested hosts. Silken Stewards are ever vigilant for Eilistraee's adherents infiltrating their ranks. Underdark-dwelling followers of Silvanus also oppose the Stewards, viewing the Stewards' methods of spider incubation and domestication as a blasphemous affront to the creatures' natural life cycles.