Ancient glyphs of elves can be found deep in the earth. Do the children of Lolth live here?
The natural formations of the earth are different here. The obelisks twist them somehow.
How far do the abyssal machines reach? All the way to the archeplaegos of Radon's birth?
The whispers of lolth travel through these halls.
Blood Sister Zaxya of the World Eaters holds the Key of Eyes and Mouths. She and her World Eater assassins hunt Black Harbingers.
High Priest Kryxsis Blacktooth attempts to channel energy from the Shadowed Keep obelisk which infuses his allies with tremendous power.
Passages in the Undercrypt lead into the caverns of the underdark.
The Black Cathedral lies beneath the dwarven citadel of Vongyth. Vongyth lies at the edge of the Forest of Grey Spires carved into a plateau.
Blood Moon goblinoids used to haunt these halls but they were subverted by the voice of the Eater of Worlds on the other side. They can be heard to whisper a word – Hethradiah.
Two lead the forces of the Black Harbinger, Sir Geldron Grayhand and Brother Navros.
Three lead the World Eaters – Blood Sisters Axleva and Zaxya and Elder Kryxsis Blacktooth.
Deep caverns lead throughout the underworld, some passages lead to the drow city of Erelhei-Cinlu. There's a nasty temple of demon-worshipping Kuo-toa down there as well.
The drow are having a bit of a civil war between noble houses – two in particular – House Kilsek and House Eilservs who now serves another deity.

Drow Houses

House of Tormtor: Actively allied with the House of Eilservs, they are very powerful despite their low rank .
House of Everhate: Nominal supporters of the houses worshipping Lolth, preferring to wait and see the outcome of contests .
House of Despana: Closely allied with Kilsek and Noquar to bring ruin upon the Eilservs, seeking to gain first precedence .
House of Noquar: Close allies of Despana and Kilsek, hoping the struggle with Eilservs will weaken their allies so they can become the greatest noble family .
House of Godeep: Committed to the anti-Eilservs faction, they seek greater rewards from the victorious Kilsek combination .
House of Aleval: A weak family primarily bent on gaining more power by waiting for either faction to become supreme and then joining the victors .
House of Kilsek: Loyal to their society of sororities and ranked second among the noble houses.
House of Eilservs: As the house of first precedence, they seek an absolute monarch to rule the Vault, turning away from Lolth and proclaiming an Elder Elemental God.

Notable NPCs

Blood Sister Zaxya holds the key of eyes and mouths.
High Priest Kryxsis of the Eater of Worlds
Sir Geldron Grayhand – wight commander
Brother Navros – Priest of the Black Harbingers but secret priest of the Dead Night
Shadowhunter Angaste Duskryn
Shadowhunter Gurina Duskryn

291 sp, 2,244 gp, 72 pp (2,993gp), 750 gp ghoulish coral bead necklace , Ring of Protection, Spell Scroll (4th-level, Death Ward), Portable Hole,

Helm Hobbs was cut down by Sir Geldrin who trapped him in his sword.
Brother Navros used a concoction to pull Helms soul into the realm of Demogorgon where the characters realized that Demogorgon is behind both the Eater of Worlds and the Dead Knight.
Voxi used a scroll of revivify to resurrect Helm Hobbs but he is marked by Demogorgon and has now “seen some shit”. He now talks to the creepy weepy doll
The characters made their way into the undercrypts to the chapel of the World Eater and are about to face a dozen World Eater goblins.