The Spiderscape (Forgotten Realms)

This is an updated version of an earlier concept.

Forgotten Realms: A Days Of Future Past-style dark future in which Lolth has devoured all but a handful of her fellow deities, leaving only a few of the most interesting to hide and wonder when it will be their turn. Lolth's dominance has is unkind. She has spun a sun-occluding cocoon around the entirety of Faerun, plunging the world into gloomy twilight. With her blessing, spiders evolve into ever more capable predators, filling ever larger portions of ecosystems. The magical Weave, the source of magic itself, is pulled taught and patterned like a web, twining around Drowish prayers and filling them with power. A spectral web stretches across the afterlife, snaring souls before they can reach their final rest and filling an already bloated Lolth with even more power. 

Non-drow or anybody that dislikes eating fungus and spiders is pretty unhappy. A few remaining deities and their followers prowl the shadows, surviving as best they can and seeking a way to defeat or escape Lolth.

The Spider’s Super-Apotheosis

Lolth has always been powerful in the Realms, but as of 1579 DR she is the uncontested superdeity. She devours, subverts, replaces, or drives off nearly every other divine force on Toril. Lolth absorbs the divine portfolios of Shar, Mystra, Kelemvor, and anybody else that you don’t feel like having around. Ao isn't pick up the phone. For the realms, this is disastrous.

The Deluded Faithful: Some of the deities killed by Lolth were replaced by her without notifying their followers. Thus, a cleric of Chauntea might still be granted spells and try to work within the newly spider-oriented ecosystem, with ever-growing madness resulting from the mental gymnastics necessary to account for their deity’s odd behavior. 

The Few That Remain: A handful of the gods have avoided meeting their end through an abundance of foresight, the zeal of their followers, or by seizing on the chaos of Lolth’s super-apotheosis to devour other deities before she can. Though normally hostile with each other, Lolth’s supremacy has made strange bedfellows of all who remain. I suggest Bane, Sune, Talos, and whatever deity your players want to play a cleric for.

The World According To The Spider Goddess

Though Lolth’s accumulation of power was perceived as a threat by most creatures on Toril, it was on the Night Of Eternal Silk that it became clear that her power was literally unmatched. On that horrid night, she slew Lathander and emerged into the sky, vast as the moon, and horrid enough to drive many mad. She spun a vast cocoon around the entire planet of Toril, muting daylight sufficiently for the Drow to withstand its effects. The cocoon also effectively severs Toril from other planes: any who attempt planar travel risk getting caught in an interplanar web and having their soul sucked out by

Webs As Weather: Many of the natural systems of the world are no longer functioning due to lack of divine maintenance. For example, most rain consists of a moist, sticky webbing, "ballooning" immature spiderlings, or venom. Photosynthetic plants are slowly dying out in favor of more fungal specimens.

Spider Magic: Lolth has co-opted much of the magical weave that surrounds Toril. Magic that matches her sensibilities is more powerful. Spells that deal with web, spiders, or poison are automatically cast at one spell level higher without any additional cost. Due to planar limitations, summoning spells do not function unless the creature they call is from the Abyss, elsewhere on Toril, or a spider. That kind of thing.

Genocide: The Drow have eradicated many of the other races on Toril. For example, there probably aren’t very many non-Drow elves left. Maybe a few hard-boiled people shuffling around a Moonblade they can't use. Perhaps a few truly powerful Eldreth Veluuthra, Another thing: I don’t know why this would come up in your game, but one example of Lolth’s far-reaching, world-destroying powers is that about one in five children born to other humanoid races are Driders with inherently evil alignment. That figure increases steadily over time.

The Players’ Dilemma

Defeating Lolth is not viable. The cities and temples of Toril’s surface are shrouded in webs and haunted by the Drow and their increasingly powerful servants. Wherever the players are hiding, they are one of the few remaining forces capable of acting in opposition to Lolth’s wishes. Maybe some survivors are driven into the Underdark, as once were the Drow.

Escape: Having cocooned the entirety of the planet, Lolth is proceeding to suck it dry. It is only a matter of time before the entirety of Toril is pulled into the Abyss. The players must find a way to pierce the cocoon and escape with as many survivors as possible.

Oghma Might Know: If I were you, I’d have the players travel to what’s left of Candlekeep to consult with what’s left of Oghma, whose drained, cocooned cadaver resides deep within that city. The city would make a pretty wicked hex crawl if you found a map of it and wrecked it. As every city, Candlekeep is watched over by a troupe of Drow, arachnids, demons, and combinations of all three. 

Moonblades, Obviously: Oghma probably thinks that moon blades are the only thing with the right sympathetic magic to cut Lolth’s sky-web. Not enough to get rid of them, mind you, just enough that one could create a gate to another plane and escape. The players will need to find a moonblade and perhaps more difficult, an elf that can wield it. I leave the details of that as an exercise for the reader.

Spiders Are Pretty Metal

Here are even more things that I think would happen if Lolth were goddess supreme:

Cannibal Drow: The dark elf women eat their males after having sex with them. I don’t know why that would come up in your game, but there it is.

Eight-Legged Blasphemies: I really like the idea of other deities’ angels being eaten alive from the inside by parasitic behavior-controlling spiders, such that they believe that they are still serving their (dead) divine patron even as they carry out the bidding of Lolth’s priestesses. I’d call them “Akkabishai”, derived from the Hebrew word for spiders. Feathery wings covered in webbing, a chunk of their skull missing, a swarm of spiders scuttling into and out of that hole, eight-eyed angels.

The Doubling: Hey, what if black widows doubled in size each generation until they were the size of buildings? Then what if the Drow used them as living siege engines? Just a thought!

Hellmouths: Making a portal to Demonweb Pits should be pretty easy at this point. I’m thinking giant crevasses whence spider-demons constantly drag themselves forth into the world. And some spidery hell-wraiths made from conglomerated souls of dead non-Drow, et ceteras.