Aracnas is a semi-wealthy trade city in The Underdark, with a very divided populace.
There are the wealthy merchant families; most of them are Duergar or Drow. They maintain the very imposing toll booth that blocks the very direct road to The Surface. They all live in the merchant houses, or in tunnel-mansions along Spider Road. In my game, I had three main families (2 Duergar, 1 Drow).
There are the "indentured servant" populace; most of them are Svirfneblin, but Drow and Duergar are present as well. Many of the indentured servants are escaped slaves or refugees that are trying to earn wages, and pay the toll that will allow them to escape to The Surface (and freedom). There are also many who are waiting (possibly in vain?) for their loved ones to meet them in Arachnas before they go topside. Many of the populace work the mushroom terraces. Indentured servants are forbidden from owning any kinds of weapons or magical items... This does not mean that they don't actually have such items.
Arachnas' economy is heavily dependent upon Surface - Underdark trade, and upon the cheap labor produced by the poorer classes. The Toll House is heavily guarded by elite mercenaries, hired by the various merchant families.
Toll House- This is a heavily-reinforced building that totally and completely blocks the road that leads to the surface. Many guards patrol the sole entrance, so as to prevent toll-jumpers. Set the toll to whatever outrageous amount you see fit.
Shopping- The shopping district is home to several curio shops, and arms dealers who will happily trade in the kind of gear that adventurers going lower will need. However, as Arachnas is regarded as the "last stop", the prices are heavily inflated, unless you are a member of one of Arachnas' trade families.
Inns- The Inn District has many fine establishments where adventurers may seek rest and information before delving deeper. The inns are mostly owned by members of the Merchant Families, and staffed by some of the better-looking refugees. However, there are one or two inns that are independent of the big Merchant Families, and are owned by lower-class 'citizens' who managed to save their money. (If your players stay in one of the independent inns, they should expect to see some kind of trouble from the "Friendly Neighborhood Protection Guild".)
Temple- There is a singular temple in this city. In my setting, it is dedicated to the Drow God Arachnas; a son of Lolth and Corellon. He is a vain, selfish, entitled and somewhat oblivious god. Although he is a "mama's boy" who is very much like Lolth, he does not permit slavery, and he does not permit escaped slaves to be returned to their masters. It is on Arachnas' orders that the poorer populace be paid wages for their work (even if the wages are a pittance). Imagine a congenitally wealthy W.A.S.P. who periodically donates to charity, purely for the sake of improving his own image.
Drow- The Drow district is mainly barracks where the Toll House guards sleep. There are the occasional town guards from other cities that show up to drag escaped slaves kicking and screaming back down below, but they are not "officially tolerated" within the city.
Merchant's Houses- This is where many of the wealthy people of Arachnas live. These houses are very fancy; most of them are carved out of the surrounding rock, or they are sprawling tunnels that wind their way deep into the Underdark.
Mushroom Terraces- A large bunch of terraces where many of the poor populace slave away, growing all varities of mushrooms for their "employers". There are taskmasters all over the place who whip slackers into working harder, and keep track of all the farming implements.
Shanty District- A sprawling, fetid area where makeshift homes and beds house all manner of refugees and escaped slaves from The Underdark. There is a very secretive black market, where many of the poorer folk trade in valuable items they have either brought with them from their homes below, or stolen from their old masters. As it is illegal for anyone outside of The Merchant Families to own magical items or weapons of any kind, you can imagine that the fear of discovery is very real for those who are in this black market.
The only way into the palace is to enter through the underground basement entrances that wind their way through the Drider warrens. Feel free to have various means of ingress either caved in, or blocked off by armed Driders so as to force your players through a specific path in the dungeon.
For the Drider stats, I either used the traditional Drider from the 5e Monster Manual, or I occasionally threw in an “Elite Drider” that had +2 AC, spellcasting and did 1.5 - 2x damage.
At the center of the Drider warrens is an immense spider web that suspends a silver, spiral staircase ~50 feet in the air. Lolth will appear in this room in the guise of an elephant-sized spider that speaks. (Up to you if she reveals herself or not.)
If the players choose to fight Lolth in this form, use stats for an Ancient or Adult Black Dragon from the Monster Manual.
Instead of a breath weapon, give her an acidic web-shot that will incapacitate a target for 1 round, and burn them for heavy amounts of damage. Bites should cause poison, instead of acid. This should not be an easy fight.
Should the players win the fight, Lolth will reveal who she is… And she will be *pissed*. She will order her guards to rip the party to pieces, and bring their mangled remains to her throne room. Lolth will then retreat to her throne room.
Your players may fly up onto the spiral staircase, climb the webs, bribe/intimidate a Drider (a difficult task, mind you!) or entreat Lolth herself to permit their entrance.
Once the players reach the spiral staircase, they may ascend to the tower proper. Near the top, the staircase will split off into two different staircases.
Path A will lead directly to an immense trap door, that leads to Lolth’s throne room. This door weighs thousands of pounds, and should not be lift-able for even the stronkest of barbarians. (Up to you though).
Path B will lead to a heavy locked door just outside the throne room. This is the access to the rest of the palace.
The door to the throne room will be locked. (Up to you if you want to permit lockpicking to open this. I personally did not.)
The players should begin exploring the palace proper in order to find the key to the throne room. Stats used for the guards were either the Driders from 5e Monster Manual, or “Dark Elf Duelist” and “Valkyrie” from Tome of Beasts.
Priests of Lolth were “Dark Elf Enchantress” from “Tome of Beasts”.
1) Tower of Domination- This is a spiraling tower full of jail cells. Many are Drow who have displeased Lolth in some manner or another. The cells are guarded by Driders and armed guards. Many of the prisoners are eventually drained of their blood, and fed to the Driders.
2) Tower of Beauty- This is a tower where Lolth keeps a harem of aesthetically pleasing male servants. Most of them are fair-skinned, and look considerably like Corellon Larethian (her ex-husband that she hates).
3) Tower of Treasure- This tower contains many booby-trapped treasures; feel free to add your favorite cursed items!
Hoard Golem, Emerald Eye, and Nagas made of treasure reside all here. Three giant spiders guard this place. They hang on the ceilings, and quietly observe the party. They only approach if the players attempt to leave the tower with any of Lolth’s loot.
4) Tower of Wisdom- This tower is a large temple to Lolth. It is tended by many of her priests, who will actively fight the players if they disturb any of the terrible rituals that are taking place. In my game, Drow must undergo a “ritual of searing pain” in order to be considered for transformation into a Drider. The party so annoyed the High Priest that he bid one of the Drider nominees to assist the party; he could imagine no greater suffering.
5) Tower of Delights- Lolth has a number of Drow children kept here. There are many toys, and comforts afforded these children. It is heavily guarded by Drow, specifically NOT Driders. Let your players interpret this place as they will.
6) Tower of Hope- The tower of hope is where Eilistraee lives. If the players treat her nicely, they can gain some insight into Lolth’s actions. Her chambers are filled with artwork, depicting the Drow at their best, Corellon and Lolth before their split, and the history of the Elven races. (To really mess with your players, put several very detailed marble statues on the first floors. They’ll think there’s a medusa upstairs.) In my setting, Eilistraee is a master artisan; a kind of Leonardo DaVinci goddess. I was originally going to hide the key beneath a treasure golem in the Tower of Treasure, but my players convinced Eilistraee to smith them a key. I did not stat Eilistraee, but feel free to use a watered-down “Queen of Night and Magic”.
7) Tower of Servitude- This is general quarters for the various slaves of the palace. Most of them are very fearful. Some have had their mouths sewn shut, ear cut off or fingers permanently broken.
8) Tower of Sacrifice- This tower is completely webbed. It is tended by several horse-sized spiders. There are a number of Drow in this tower that are undergoing their grisly transformation to Driders.
9) Throne Room- Lolth’s throne room. The entire floor is covered in webbing, and counts as difficult terrain. Lolth will be seated on her throne, in her ‘true form’. (In my setting, that means she is a 7ft tall Eladrin with black skin, white hair and bright, blue eyes.) I used the stats for the “Queen of Night and Magic” from the Tome of Beasts; her speed is doubled when she is walking on webs.
Feel free to decorate the throne room as you see fit.
Monsters Used -
Drider 120 (MM)
Guardian Naga 234 (MM)
Duelist 171 (ToB)
Enchantress 172 (ToB)
Emerald Eye 175 (ToB)
Queen of Night and Magic 192 (ToB)
Hoard Golem 234 (ToB)
Valkyrie 396 (ToB)