These cities are listed from the closest to the surface to the deepest beneath the earth.
Cities 1-3 are in the Overdark, a cold and dank area where the surface dwellers often feel the most comfortable.
Cities 4-8 are in the Underdark Proper, with tunnel highways that are home to bison-sized mushroom-beasts and heated by lava.
City 9 is in a hollow earth jungle, heated by an Illithid-made sun.
City 10 is in the Underdeep, said to be so far underground that planar travel occurs when going that deep and underworlds are easier to contact.
Culicid: a castle town ruled by a vampire, a veteran of the war and self-styled duchess. She collects blood as taxes – the blood-tithe. Culicid has the largest population of free humans beneath the surface, policed by the duchess’ immortal children.
Exports: bio-luminescent mushrooms, messenger bats, goats
Xenosh T’allotha: In Drow this means, All-Mother’s First Rest, as it is the first place the Drow stopped to rest during the exodus from the skylands. It is a small town, really a village built around a series of wells and underground waterfalls that has grown out into the tunnels that lead to it.
Exports: Religious artifacts, Riding spiders, Monk bodyguards
Anvil: The decrepit holdfast that houses the dwarves who sided with the underground armies. It is ruled by a council of petty dwarven princes who have been trying to elect a High King since the war ended. Some whisper that outside political pressure has thwarted this process.
Exports: Mead, dwarf-made weapons and armor, dwarf-cut gems
Titan: The Githyanki fortress city built from the buried fossil of a forgotten lizard demi-god is watched closely by the Drow matriarchs. The Githyanki were allowed to keep control of this city after their attempted coup under the watchful eye of a powerful Drow priestess, along with sending hostages to Endë-Osto and their sleeping red dragons were hidden from them.
Exports: Dream-walkers, Swords-for-hire, Warlocks-for-hire, Domesticated Umber Hulks
Quaggothan: More of a meeting place or a camp site than a proper city, this is the ancient site where the Quaggoth elders live out the last days of their life when they can no longer follow the mushroom herds. It is ruled by a Drow-appointed governor who oversees the trading and make sure the Quaggoth feuding never gets out of hand. Merchant caravans always stop here to trade their foods and it has become a hub of trade and news.
Exports: Mushroom bison meat, odd artifacts the Quaggoth unearth in their travels
Kitji-Naal: Two cities divided by an underground river and ruled by twin matriarchs who rarely meet, but communicate via magical mirrors. The city is the largest and most populated city in the underdark; its politics are a convoluted mess of ancient feuds, assassin’s knives and inter-House warfare.
Exports: Poisons, Assassins-for-hire, spider-silk, books
Sclera: A dank, and dangerous city ruled by feuding gangs of Beholders – each with its own Eye-cult. This is the city with the highest human population in this layer of the underdark. It also boasts the underdark’s only public temple to Asmodeus, the Devil-God.
Exports: Scrying, mirrors, spies, indentured-devils
Eämbar: A newly founded city that is a port, connected to the ocean by a series of complicated crystal locks that link Eämbar to the ocean’s crushing depths. All manner of undersea sentient can been seen on the city streets, sometimes in specially made tanks of water pushed by servants.
The matriarch is the youngest to ever hold the title and the most renowned swords-Drow in the underdark.
Exports: Fish, undersea crafts, spider-silk crystal
Endë-Osto: The deepest city of the Drow and the Drow capital, is ruled by the eldest matriach whose throne is said to float weightless in the center of the earth. Her queensguard is made of the most cunning of the drow sword-maidens; they ride dinosaurs bred for traversing tunnels. The city is in a hollow-earth with a bruise-purple sun, said to have been created at the height of the Iillithid Empire.
Exports: vegetables, dinosaur steeds and ranger-guides
Svinifrilijihirim: Despite Endë-Osto being at the center of the world, this Gnomish city is still somehow deeper, due to a trick of planar geometry. The city, often called Deeptown for short, is home to a powerful ward, created to keep a Pit Fiend in the uninhabited darkest depths. The Pit Fiendwas unleashed by the skylanders into the underdark during the War, has destroyed a Drow city single-handedly.
Deeptown is home to a powerful council of wizards and it is a great city for finding tutoring or for apprenticing one’s self to any of the Schools of Magic. It does boast the underdark’s only Bard College that is home to one of the finest libraries in the underdark, rivaled only by Kitji-Naal and Endë-Osto.
Exports: Wizards-for-hire, Bards-for-hire, magic items, spell components
And once you’re done and you want to make the place a political mess – A Web of Cities.