Waterdeep/Sewers

The sewers of Waterdeep were a sanitation system of tunnels beneath the city that connected to most locations throughout the city, including its dungeons.

Structure
The depth of these sewers varied around Waterdeep, due to Mount Waterdeep and the plateau the northern portion of the city was built upon. The Field Ward, the harbor islands, and the heart of Mount Waterdeep were the only areas in the city that the sewers did not run beneath. With some areas having around two to three sub-levels.

Partially due to city’s ever changing layout, the tunnels of this sewer system did not match up with the routes of the city's streets by the 14 century DR.

Functionality
Refuse, as well as air, were brought down into the sewers by numerous feeder pipes scattered throughout. These pipes measured less than in diameter.

The sewer network operated on a system of tidal flushing, meaning that its waters were flushed out by the ocean tides that came into Deepwater Harbor. The sewer's tunnels emptied into the harbor at places that were covered by extremely large and strong gratings. These places were purposely difficult to access, as the sewer network's designers sought to hamper the movements of less desirable visitors from the sea and to prevent the sewers from being used by criminals as an underground highway.

The areas in which the sewer network was constructed at, as well as the varied sizes within, were designed to optimally account for the ocean tides. Their layout was also dictated by where springs rose and flowed down to the sea. And finally, due to the city's great size, Ahghairon and other mages bound spells into the city's wards and bound some elementals. These both assisted the flows of water in carrying away sewage, thereby ensuring that the city's harbor did not become a cesspool.

Some areas of the sewers featured doors that would close upon water entering from a certain passages, ensuring flooding did not occur. Others had pressure plates that would close doors once water stopped flowing over them, preventing backwash.

Construction
The ceilings, floors, and walls all throughout the sewer system were made of masonry. There was little to no lighting within the sewers and a terrible stench pervaded the entire network.

Gratings in the sewers were all made of iron and quite thick. Some were permanently set into the stone walls, while others could swing open on pivots. By the 14 century DR many were suffering from rust.

Passages
The passages of this sewer network had no names, thus directions tended to be given in terms of entry points and paces. Those who worked in the sewers were known to navigate passages by laying down boards as temporary bridges or by vaulting across ledges with catchpoles. The latter of which were carried in order to reach below the water and clear debris from gratings.

Passages were denoted as being either one of two types based on their size, primary and secondary. Primary passages were easily navigable. They measured across and had parallel,  wide, walkway ledges that lacked rails. Secondary passages were smaller, requiring human-sized creatures to crawl or swim their way through. They measured and had on one of their sides, usually the more easterly or southerly side, a single  wide ledge.

Besides these two types there were many older, smaller passages that had over time been put out of service and walled up by the 14 century DR.

Portals
Some areas of the sewers featured stone portals, a network built by an old dwarven kingdom to quickly move about. These required special enchanted stone items to activate, which took a variety of forms. These included daggers, gemstones, holy symbols, medallions, necklaces, orbs, rings, and scepters.

Some areas featured teleportation pads that were constructed by the sewer network's designers. These would teleport people to the surface, acting as an emergency exit for sewer workers in the case of flooding or other hazards. When broken, they would only teleport people elsewhere within the sewers.

Interior Connections
The sewer network notably featured connections to the dungeon complex under Castle Waterdeep, the Dungeon of the Crypt, and in several places Undermountain. Many such links were kept operable and secret by the many guilds and shady organizations that operated in the city.

Connections with Undermountain in particular featured heavily in the city's tavern lore.


 * Dungeon Level: This first level of Undermountain had a tight winding crawl space, the Grim Passage, that ended at a secret door high above the headless relic known as Grim Statue. This was entered by means of a hidden door in the sewer passage beneath Slide Alley. The Grim Passage wound and twisted through the rat-infested remnants of old, filled-in and forgotten cellars and disused privy chutes, until curving into a dead end where the hidden door above the statue laid. The drop down to the Grim Statue was roughly.
 * Lost Level: This sixth level of Undermountain was connected to the sewers by means of a portal that was visible only on the night of a full moon in the month of Flamerule.

Sewer Ecology
There were a great deal of creatures that inhabited this sewer network, far more than could logically be expected to find enough food to survive. Many of these creatures entered the sewers by means of the Dungeon of the Crypt and Undermountain. There was a small chance of oozes crawling their way up the privy pipes of the sewers.

Adventurers, wizards-for-hire, and mage guilds were regularly hired to go into the sewers to sweep and clear monsters out of areas.

The creatures most commonly encountered within the sewer network around 1357 DR included: huge centipedes, a colony of green slime, a colony of yellow mold, mites, rats and giant rats, rot grubs, and scum creepers.
 * Around 1357 DR

The creatures less commonly encountered in the sewers around this time were: boggles, galltrits, giant bats, giant centipedes, giant ticks, huge spiders, jackalweres, large pedipalps, mongrelmen, skeletons, stirges, and wererats.

And finally, the creatures only rarely encountered in the sewers around this time were: cambions, giant bloodworms, cave fishers, crocodiles, executioner's hoods, giant slugs, gibbering mouthers, gorbels, grells, lurker aboves, mimics, neo-otyughs and otyughs, obliviaxes, shadows, shadow demons, shambling mounds, slicer beetles, stunjellies, tentamorts, tunnel worms, vargouilles, and xorns.

The creatures most commonly encountered within the sewer network around 1368 DR included: bats, crocodiles, giant leechs, otyughs, megalo-centipedes, mongrelmen, ochre jellies, osquips, rats and giant rats, rot grubs, skeletons, slithering trackers, stirges, stun jellies, tunnel worms, yellow molds, and zombies.
 * Around 1368 DR

The creatures less commonly encountered in the sewers around this time were: broken ones, brown mold colonies, cavefishers, gremlins, sewerms, shriekers, giant spiders, giant and huge centipedes, gray oozes, green slimes, and russet mold colonies.

And finally, the creatures only rarely encountered in the sewers around this time were: carrion crawlers, cave fishers, deepspawn, common feyrs, giant slugs, gorbels, green hags, grells, gulguthydrae, jackalweres, living walls, lurkers, mimics, shambling mounds, and sinisters.

The creatures most commonly encountered within the sewer network around 1372 DR included: bats, bloodbloaters, carrion crawlers, centipedes, chokers, eyeballs, common feyrs, flotsam oozes, gray oozes, gricks, lurkers, meazels, merfolk, mimics, ochre jellies, osquips, rats, sewerms shadows, shriekers, skum, spiders, splinterwaifs, stirges, twig blights, violet fungi, wasps, and wererats.
 * Around 1372 DR

The creatures only rarely encountered in the sewers around this time were: aboleths, beholders, breathdrinkers, chuuls, crimson deaths, cursts, crocodiles, darkmantles, darktentacles, deepspawn, drowned ones, ghaunadans, gibbering mouthers, greater feyrs, greenvise, grells, gulguthydrae, kelp anglers, leechwalkers, lifeleech otyughs and normal otyughs, mongrelfolk, moonrats, mudmaws, ocularons, plague ants, plague spewers, shambling mounds, sinisters, swamp striders, wights, will-o'-wisps, wraiths, and yellow musk creepers and zombies.

Surface Shafts & Junction Rooms
Some areas connected between primary passages, known as junction rooms, were square in shape. They measured by, were  tall, and had a sitting ledge near their ceiling.

Entrances into the sewer network were known as surface shafts. They measured in diameter, were typically spherical in shape, and had iron rungs set in the walls for use as ladders. They were capped by covers made either wholly of metal or of metal-banded wood. These covers were known as "manholes" or "person access covers."

The surface shafts and junction rooms of this sewer network (as labeled on the map above) could be found at the following locations:
 * SF1: A surface shaft underneath trees in the interior of the block northwest of the shrine to Silvanus within the Shrines of Nature.
 * SF2: A surface shaft in the northernmost corner of Sabbar's Alley.
 * SF3: A surface shaft in the center of Shank Alley.
 * SF4: A surface shaft south off the Street of Glances and just south of the tree in Sniff Alley.
 * SF5: A surface shaft in the central stand of trees in the southern end of Heroes' Garden. Halfway down this shaft was a secret entrance leading to the Catacombs of Yintros.
 * SF6: A surface shaft under a lone tree in the alleyway west of Eltorchul Villa, south of Ivory Street and north of Pharra's Alley.
 * SF7: A surface shaft in the mouth of an alleyway opening north off Chasso’s Trot, just west of Sul Street.
 * SF8: A surface shaft in a cul-de-sac due south of Jhansczil Villa.
 * SF9: A surface shaft underneath a tree, in an alleyway just south of Brossfeather Villa.
 * SF10: A surface shaft just south of the Ilitul Villa, at the northern end of a dead alley opening off Grimwald’s Way.
 * SF11: A surface shaft just west off Mendever Street, in the easternmost cul-de-sac that opens off the alleyway bounding Nesher Villa.
 * SF12: A surface shaft in an alleyway just west of the gates of Manthar Villa, off Delzorin Street, between Sul Street and Shield Street. Opens into a junction room.
 * SF13: A surface shaft in the alleyway within the block surrounded by Copper Street, Delzorin Street, the High road, and Vordil Street.
 * SF14: A surface shaft in Trollskull Alley, southwestern corner, near the intersection of Delzorin Stret and Whaelgund Way.
 * SF15: A surface shaft in a cul-de-sac north of Horn Street, between Tower March and Whaelgund Way.
 * SF16: A surface shaft at the intersection of Sharra's Flight and the Street of Whispers.
 * SF18: A surface shaft in a cul-de-sac opening northeast off of Toalar's Lane.
 * SF19: A surface shaft at the intersection of Calamastyr Lane and Gothal Street. Opens into a junction room.
 * SF20: A surface shaft at the southwestern corner of Runer's Alley.
 * SF21: A junction room without any surface entrance, located under the southern mouth of Cloaksweep Alley.
 * SF22: A surface shaft in a copse of trees at the center of a block bounded by Copper Street, Hassantyr's Street, the High Road, and Julthoon Street.
 * SF23: A surface shaft at the western end of Marlar's Lane.
 * SF24: A surface shaft at the base of a rocky cliff-face, just behind Blackstaff Tower.
 * SF25: A surface shaft near the top of the rocky slope of Mount Waterdeep, at a point due southwest of Turnback Court.
 * SF26: A surface shaft located in Turnback Court. Opened into a junction room.
 * SF27: A surface shaft located in the southwest corner of an alleyway that opened south off Cymbril's Walk, at the intersection of Street of Silver and Warriors' Way.
 * SF28: A surface shaft located in the southwest corner of a dead-end alley, in the block bounded by Lamp Street, the Street of Bells, Cymbril's Walk, and the Street of the Sword. Opened into a junction room.
 * SF29: A surface shaft located at a northwestern junction of alleyways, in the block bounded by the High Road, Lamp Street, Selduth Street, and the Street of Bells.
 * SF30: A surface shaft located at the southeastern corner of an alleyway, opening off the High Road and to the west of Andamaar's Street.
 * SF31: A junction room without any surface entrance, located beneath the Grinning Lion tavern.
 * SF32: A surface shaft located at the northwestern corner of an alleyway, opening off Golden Serpent Street and Nindabar Street.
 * SF33: A surface shaft located at the halfway point of Belzound Street.
 * SF34: A surface shaft located at the northern mouth of an alleyway that opened off of Sevenlamps Cut.
 * SF35: A surface shaft located at the intersection of Lemontree Alley and Shadows Alley.
 * SF36: A surface shaft located in an alleyway just north of the Pampered Traveler inn.
 * SF37: A surface shaft located in the wide alleyway between the High Road and the Street of Bells.
 * SF38: A surface shaft beneath the House of the Fine Carvers, leading into a junction room.
 * SF39: A surface shaft located on Spindle Street.
 * SF40: A surface shaft located on the lane that paralleled Irimar's Walk.
 * SF41: A surface shaft located in an alleyway that opened west off of Wall Way, just south of Andamaar's Street.
 * SF42: A surface shaft located in an alleyway that opened west off of Wall Way, just north of Ironpost Street.
 * SF43: A surface shaft located within a copse of trees, in a dead-end alleyway just north of the Costumers' Hall.
 * SF44: A surface shaft located at the mouth of a dead-end alleyway that opened east off of the Street of the Tusks.
 * SF45: A junction room without any surface entrance, located beneath an alleyway that opened south off of Spendthrift Alley.
 * SF46: A surface shaft located within the cellar of the Unicorn's Horn.
 * SF47: A surface shaft located in the alleyway behind Olmhazan's Jewels.
 * SF48: A surface shaft located at the end of a dead-end alleyway, which opened south off of Nelnuk's Walk.
 * SF49: A surface shaft located in the southwestern corner of a dead-end alleyway, which opened off of Shesstra's Street.
 * SF50: A junction room without any surface entrance, located beneath the westernmost section of alleyways that opened off of Snail Street.
 * SF60: A surface shaft in a in a cul-de-sac opening, east off the northern end of Drovers' Street.
 * SF61: A surface shaft located at the halfway point of Beacon Street.
 * SF62: A junction room without any surface entrance, located under the intersection of Grocer's Lane and Snake Alley.
 * SF63: A surface shaft in Rednose Alley.
 * SF64: A surface shaft located in a cul-de-sac opening off the Rising Ride, between Caravan Court and Juth Alley.
 * SF65: A surface shaft located in the widest part of the alley that opened south off of Olaim's Cut.
 * SF66: A surface shaft located in the wide alley north of Coach Street and west of the High Road.
 * SF67: A surface shaft located east of Carter's Way and south of Coachlamp Lane.
 * SF68: A surface shaft located in the cellar of the Spouting Fish tavern.
 * SF69: A surface shaft located on the second alleyway north of Bellister's House.
 * SF70: A locked surface shaft within the cellar of Piergeiron's Palace. It was guarded at all times by five City Guard and an armar. Whenever they saw or heard anything suspicious from the sewers, they would sound alarm on the wall.

Areas not labeled on the map included the following:
 * Golden Hammer: An inn with a trapdoor that opened into the sewers.
 * Jalanvaloss: This steel dragon had secret apartments in the House of Pride and Meiroth's Fine Silks that had entry stairs linking to the cellars, which linked to the sewers. They also had a secret cache somewhere within the city.
 * Safehaven: An inn in the Southern Ward, whose cellar contained a hidden ladder leading down to the sewers. This ladder was hidden behind a tall door, which opened upon turning upward the spigot on the last wine casket.

Groups of Interest

 * Cellarers' & Plumbers' Guild: Most members of this guild learn the general layout of the sewers after two to five years. This is because their primary concerns were keeping the sewers of the city functional and safe, with guild members being engaged in constant small repair jobs in the sewers, such as on plumbing in old buildings.
 * City Guard: In the late-14 century DR, it became the duty of the City Guard to police the sewers.
 * City Watch: Up until the late-14 century DR, it was the duty of the City Watch to police the sewers. After this authority switched over to the City Guard, watchmen rarely ever entered the sewers. Only doing so if pursuing a suspect or when they discovered sewer tunnels that connected with cellars.
 * Confluence: The lower status members of this secret society used secret passages within the sewers to enter Tespergates, their organization's base of operations, by means of the villa's cellars.
 * Dungsweepers' Guild: This guild normally did not work on the sewer system, but for security reasons the city reserved the right to contact the guildmaster and hire members to help in such work.
 * Guild of Watermen: Members of this guild knew various spots where the sewer system emptied into the harbor.
 * Merfolk: Living within Deepwater Harbor, these people regularly patrolled the areas where the sewers emptied. They would use pole mounted catch-nets to scoop up and gather any debris they found into large tow-globes, which they then used to transport the debris far out to sea.
 * Plague Rats: This elite organization of thieves and assassins operated mainly under the cover of darkness in this sewer network and the Dock Ward.
 * Savants of the Dark Tide: This aboleth-led criminal organization had its base of operations within this sewer network and mainly operated within it.
 * Unseen: This secret society operated out of both the sewers and Rat Hills for decades, but following the Rat Hills Conflagration they began having their main meetings within secret rooms in the sewers. Their leader, Hlaavin, also kept many safe houses within the sewers.
 * Xanathar's Thieves' Guild: This guild had safehouses scattered throughout the sewers, hidden by secret doors. Tunnels were often marked with the symbol of the guild in yellow chalk, helping to guide members to the safehouses. Every few days these were erased, either by members of the guild or by the Dungsweepers' Guild. The guild also utilized some of the stone dwarven portals that were scattered around the sewers.

History
These sewers were built over the course of many generations.

During the days of Ahghairon, a number of Underdark creatures tried to invade the sewers and Waterdeep proper by means of a portal within Undermountain, which he put an end to by means of the gatewarp spell.

At some point a group of dwarves established a kingdom beneath the sewers, which eventually fell into ruin and became a mere legend on the surface. Their ruins were later discovered by Wently Kelso and the would-be Heroes of Waterdeep.

In 1358 DR, during the Time of Troubles, the mortal avatar of Myrkul opened a portal between Hades and the Prime Material plane. Hoards of undead came rushing out through the sewers and up into the Dock Ward. The guardsman Ylarell tracked these undead and in the process was slain by Myrkul. Five Cellarers also became lost in the sewers during this time, having been transformed into cursts that continued to patrol the sewers for decades.

In the wake of Myrkul's destruction a deathshrieker was created in the sewers beneath what later became known as Cynosure. It would stalk the sewers for over a decade.

In Eleint, 1367 DR, new creatures began to be encountered in the sewers by members of the Plumbers' Guild, such as sewerms. Some of these new creatures originated from the Rat Hills, such as gulguthydrae, having fled into the sewers following the Rat Hills Conflagration.

In 1369 DR, during the event known as Halaster's Higharvestide, a number of creatures crawled out from the sewers and terrorized the people of Waterdeep.

That same year the city faced an attack by the forces of Iakhovas. In the wake of that repelled invasion a number of sea creatures escaped into the sewer system, with some of them, like the malenti Laaqueel, having been led into the sewers through a surface shaft at Coin Alley by Iakhovas himself. Among the dozens of aboleths that fought in the invasion one trio, hailing from the Swordsea Depths, had joined in this assault for the sole purpose of using the chaos to sneak their way into the city's sewer system in pursuit of the fabled Sargauth Swimmer. Within the sewers the would-be Savants of the Dark Tide established a lair, then over time gradually enslaved members of the Cellarers’ & Plumbers’ Guild and transformed rogues into skum servitors.

Around 1372 DR, the doomsphere Xliiqil began stalking the sewers, trying to learn what happened to the Company of Crazed Venturers who had slayed it decades prior.

In 1492 DR, Jeryth Phaulkon sent awakened rats into the sewers to search for Xanathar's hidden lair, eventually discovering a secret spiral stairwell in the sewers beneath the Castle Ward.

Rumors & Legends

 * Some rumors claimed that the cellars of some of the City Watch's guardposts contained secret entrances to the sewers.
 * There were persistent rumors that Uluryk Malogh made an extensive map of the city's cellars and sewers, detailing all their various barriers, locks, and traps.
 * Around the mid-14 century DR, there were rumors circulating that Xanathar's Thieves' Guild had trained guard rats roaming the sewers and that slavers dwelling within the uppermost rooms of Undermountain creeped out into the sewers at night to kidnap unsuspecting Waterdhavians.

Appearances

 * Adventures
 * Waterdeep • Dungeon #30, "...And a Dozen Eggs • Undermountain: The Lost Level • Dungeon #126, "The Blood of Malar" • Halls of Undermountain • Dungeon #206, "Eyes on the Ball" • Waterdeep: Dragon Heist
 * Undermountain: Stardock • Expedition to Undermountain
 * Novels
 * Waterdeep • Escape from Undermountain • The Abduction • The Diamond • Rising Tide • Silverfall, "Lady Cassalanter’s Busy Day" • Daughter of the Drow • City of the Dead • The God Catcher • Circle of Skulls • Timeless
 * Windwalker • The Shadowmask • The Ghost King • Elminster Enraged
 * Video Games
 * Eye of the Beholder • Descent to Undermountain • Dungeons & Dragons: Eye of the Beholder
 * Organized Play & Licensed Adventures
 * The Map with No Names • Dock Ward Double-Cross
 * Organized Play & Licensed Adventures
 * The Map with No Names • Dock Ward Double-Cross