Drow feature as a fairly large antagonist in Dungeon of the Mad Mage, but their lore has always rubbed me the wrong way. No society should be entirely, universally evil. But I still wanted to use drow as villains. So what did I do? I rewrote drow lore a bit. And to fill you in with how I'm going to handle drow from now on, I'm going to do what I do best, I'm going to tell you a story. A story of the ancient past, of centuries of scheming. A story of the elves.
A long, long, long time ago, too long ago to properly determine, the elves were united under Corellon. Their forms changed on a whim like their primary deity's did as they wandered the world. Lolth was second in command of the elven pantheon, a position she held with silent determination. Unfortunately, this relative peace wouldn't last. You see, it kind of sucks being second in command, especially when the first in command hardly seems to make any decisions. Corellon is a mercurial deity, wandering about, taking various forms, but never seeming to have a plan to elevate the elves. If Lolth were in charge, she could bring about a golden age of the elves. At least that's what she thinks. But Corellon would never agree to this. He is content to let his whims carry him and the elves for all eternity. So, Lolth sits back and schemes. She has all the time in the multiverse.
She schemes, and schemes, until she puts together a plan. Out there in the Outer Planes is the infinite Abyss. This plane of pure chaotic evil corrupts all that its denizens, the demons, get near. With enough powerful ones on the Prime Material Plane, the whole plane could be corrupted and dragged into the Abyss. If Lolth were of the Abyss and went through this corruption process she could wrest control of the plane not just from Corellon, but from every other power of the Prime Material Plane. A web begins to form.
Lolth carefully convinces other elven deities, among them Ghaunadaur and Eilistraee, to follow her on a journey to claim a new domain for the elves: the largely unexplored Underdark. She convinces them that the elves could be the first to claim this unconquered and dangerous domain if Corellon could ever make up his mind about anything. Convinces them that she would make a better ruler of this new group of elves. A web is woven, a plan to split from Corellon is made. Wilfully neglected is a plan to rub it in Corellon's face as Lolth is slowly corrupted by the chaotic essence of the Abyss.
And so, the plan is set into action. Lolth takes the permanent form of a spider because Corellon always hated them and publicly dares him to defy her and her new followers, attempting to trap the primary elven god in webs so as to make her escape. However, Corellon's shifting form causes this plan to backfire. What Lolth fails to realize as the planar essence of the Abyss corrupts her, a thirst for untold violence and destruction, is that Corellon is capable of great tactics when provoked. A battle takes place as Lolth, a great battle between gods. Unfortunately Lolth had failed to inform the other deities she had been leaving with of her plan to rub this in Corellon's face, so she was alone against him as Ghaunadaur and Eilistraee safely ferried the elves that would become the drow deep beneath the ground into the Underdark.
The battle ends with Corellon deciding on a semi-permanent form, that of modern elves, to battle Lolth in and Lolth being pushed to activate a failsafe. As one final act of the battle, Lolth's webs tear open a portal to the Abyss, which she flees to so she can live to scheme some more. Finally in the Abyss, Lolth absorbs some of its essence to become a demon lord and claims one of its infinite levels for herself, naming it the Demonweb Pits.
The Abyss is a tear in the fabric of reality, infinite layers filled with creatures that seek only to destroy and corrupt. Most of these monsters are embroiled in the plane spanning Blood War between the chaotic evil demons of the Abyss and the lawful evil devils of the Nine Hells. These planes both desire to subjugate the multiverse but are at odds with each other, each keeping the other distracted. Lolth, a being from outside of the Abyss, is not distracted by such things, and can bring corruption and chaos directly to the Prime Material Plane if she has followers to do it with. Unfortunately, this is where the hole forms in her web.
As Lolth battled with Corellon on the surface, Ghaunadaur and Eilistraee brought the soon-to-be drow down into the strange magics of the Underdark. In short order they had chosen permanent forms as well, forms fit for life underground. Better vision in the dark at the cost of sensitivity to sunlight, primarily. Eilistraee, with her domain of dance, gifted each drow with the Dancing Lights cantrip to light their way, so they could see in color. They soon, well, soon in the terms of a godly tale, settled in underground, farming mushrooms and strange creatures, setting up clear paths through the dangers of the place, allowing strangers to stay in their cities at Eilistraee's behest and trading special goods with the surface.
Ghaunadaur, meanwhile, was furious with what he beheld. Lolth was reckless with what she had done, acting with uncharacteristic malice. He spent a long time determining where Lolth went after the battle, as she had disappeared from the face of the plane. The only subtle hints to her presence were the spiders that seemed to take a liking to the drow, who had since settled in underground. When Ghaunadaur discovered Lolth had moved to the Abyss of all places he became somehow more furious. She had placed all of these elves in danger and then fled to a plane of chaotic evil?! What for?
He confronted Lolth in the Demonweb Pits to determine why she had deceived so many, and to see if she would atone. But Lolth's true plan became clear as she laughed in his face, it wasn't expansion or taking over a new, unexplored territory for the elves she wanted. It was a plan to wrest the Prime Material Plane from where it laid, a product of the Inner and Outer Planes, and drag it into a land of violence and chaos where Lolth was in charge. Ghaunadaur lashed out at the new Spider Queen, but he was challenging a demon lord in her own domain, and Lolth had already been the second most powerful elven deity. He was outmatched. Lolth struck Ghaunadaur so fiercely that his divine essence was shattered and warped. Whatever portfolio and appearance he had once had was long gone. Ghaunadaur became That Which Lurks, referred to as such so as not to draw its unwanted attention by using its name, a god of slimes and oozes in the Underdark.
Eilistraee and the drow wept for their lost god, and Lolth's plan became clear. She sits in the Demonweb Pits and schemes to that end. Those schemes come to the modern Prime Material Plane in the form of rare cults of Lolth, consisting of drow that buy into Lolth's plan to overturn the plane and place herself and the drow in charge. The cults are cast out of the Underdark when they are discovered, which is how the cults in Undermountain got there. Most drow are content to live underground as crafters, traders, and farmers. Though they can't shake the spider aesthetic because Lolth wants them to return to her and continue her schemes.
In summary, I hope this lore works better than the default, because I don't like the idea that a race is inherently evil. Eilistraee is the current primary deity of the drow pantheon, a goddess of hospitality, dance and song. The drow, instead of being inherently bad, are caught in the schemes of a planar being. This still allows them to be villains, but it's because there is a demon lord out there who specifically wants drow, and not because they're all bad. They stay underground because the sun hurts their eyes, and welcome outsiders because they know how harsh the environment is in the Underdark. Other drow deities can be included as needed but modified in such a way that they're less terrible. As a rule, none of them side with Lolth. The one eight armed warrior god? Is now an example of how drow defend themselves from the threats of the Underdark's creatures, rather than being tied up in the Demonweb Pits or whatever. I hope you like this, the story kind of got away from me. I'd love to know what you think!