Out of the Abyss, the main published adventure for the next storyline season of D&D, is now available for pre-order on Amazon.

Here’s the descriptive text:

Dare to descend into the Underdark in this adventure for the world’s greatest roleplaying game
 
The Underdark is a subterranean wonderland, a vast and twisted labyrinth where fear reigns. It is the home of horrific monsters that have never seen the light of day. It is here that the dark elf Gromph Baenre, Archmage of Menzoberranzan, casts a foul spell meant to ignite a magical energy that suffuses the Underdark and tears open portals to the demonic Abyss. What steps through surprises even him, and from that moment on, the insanity that pervades the Underdark escalates and threatens to shake the Forgotten Realms to its foundations. Stop the madness before it consumes you!
 
A Dungeons & Dragons® adventure for characters of levels 1–15

The release date is September 15th, 2015.

Menzoberranzan is the major city of the drow, the dark elves. In D&D lore, the elves had a great war a very long time ago, which ended up with them casting out their evil brethren. The dark elves retreated beneath the surface into the Underdark and started worshipping Lolth, the demon-queen of spiders. In the Forgotten Realms, where this adventure is set, Lolth is also a goddess, not a mere demon.

The city of Menzoberranzan is (in many ways) the Forgotten Realms version of Erelhei-Cinlu, the original Vault of the Drow. Menzoberranzan was named by R. A. Salvatore when he created Drizzt, and has been revisited many times by Salvatore and other authors. The novel Homeland is the earliest work to be fully set in Menzoberranzan, and it also has the first appearance of Gromph Baenre. The city was released as a D&D supplement in 1992 for the AD&D 2E game, and again for the D&D 4E game in 2012. This last work is set about 10 years (1480 DR) before current events in the Realms, and so is fairly accurate in its description of the city, although the 2E version is a touch longer (and a lot harder to get). The 4E version can still be found on Amazon.

Basically, the drow are divided into various noble houses and their servants. The nobles constantly feud for power. The culture of the drow elevates women above men, with (traditionally) female drow being clerics and male drow being wizards; both can be fighters all rogues. The drow often consort with demons, and it seems that in this adventure Gromph Baenre manages to surpass even the normal method of contacting the Abyss – which is unlikely to be good for most involved.

How many noble houses? Lots. Only the top 20 are given in the most recent source (along with a handy chart showing their rise and fall over the past 300 years or so). Head of them all is House Baenre, which is ruled by Matron Mother Quenthel Baenre, High Priestess of Lolth.