What If Lolth Died?

[Irennan]

The early editions (1e, I think?) had Lolth being killed in her home realm, and yes, dying. It didn't explore the consequences of it, though. In theory, defeating a deity in their home realm is the only way of killing them, but deities can have contingencies allowing them to survive anyway (take Mystra and her surviving Cyric's murder attempt, though severely weakened for a century, as we see in Elminster Enraged).

As for the consequences on the Lolthite drow, it's quite easy. Without having any power to maintain the status quo, since most drow commoners are frigging' miserable, since males are friggin' miserable, since other groups (wizards, followers of other Dark Seldarine) are totally unhappy with the system but still retain their power, Lolth's matriarchy will likely get removed in a series of bloody wars. Even then, it's also likely that various factions of Lolthite drow will go against each other as well, leading to a total collapse of the society as a whole (and to other Underdark races also intervening and giving the coup de grace). If you ask why they won't come together and negotiate after the matriarchy is dealt with, remember: the Lolthite are the same guys who thought that trying to kill your own commanders in the middle of a battle is a good idea, and that preparing to backstab each other in the middle of being sieged by someone who wants to wipe you from the face of the planet was a stroke of genius.

That said, the followers of Vhaeraun might channel the rage of the drow against the matriarchy and avoid the subsequent series of wars I mentioned above. The followers of Eilistraee would likely go to rescue people caught in the middle of the disaster and bring them to safety (but to be honest, and if the worldbuilding of the drow cared to explore the consequences of its own premises even in the most superficial manner, splinter movements, and revolutions would have already formed, and Lolth's system would have already either change or collapsed over friggin' 12k years of absolute nonsense, even without her death).

As for the portfolio, the death of a deity doesn't necesaarily mean that the portfolio will pass to someone else. It's really up to you.