Waterdeep/Sewers

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

"It’s a trip neither pretty nor pleasant, but delve the sewers if you truly want to learn what goes on in Waterdeep."

- Down the Drain: A Life in the Guild of Cellarers and Plumbers, 1356 DR

Structure
The depth of these sewers varied across Waterdeep, with some areas having around two to three sub-levels. One reason for this was Mount Waterdeep and the plateau the northern portion of the city was built upon. Another was that the varied sizes and areas in which the sewer network was constructed at were both deliberate design decisions, made in order to optimally account for the ocean tides.

The tunnels of this sewer system did not match up with the routes of the city's streets above them by the 14 century DR. This was partially due to the ever changing layout of Waterdeep, but also because the sewer's layout was dictated in part by where Mount Waterdeep's springs rose and flowed down to the sea.

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.

Functionality
Refuse, as well as air, were brought down into the sewers by numerous feeder pipes scattered throughout the city. These pipes measured less than in diameter. Thanks to the pipes, air supply was good in the sewers and those who traveled in them had little chance of suffocating.

The sewer network operated on a system of tidal flushing, meaning that its tunnels were filled with water by the ocean tides that came into Deepwater Harbor and were flushed out by those same tides. The sewer also received water from its upper levels by means of street runoff of rain and the frequent coastal fog, as well as spring water that was directed into cistern-caverns in Mount Waterdeep's upper reaches and then flowed down through pipes into the various wards. 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.

Due to the great size of Waterdeep, there were concerns that the tidal flushing system could lead to the city's harbor becoming a cesspool. To ensure this didn't occur, Ahghairon and other mages bound spells into the city's wards and bound some elementals. In conjunction with the deliberate design decisions made for the sewer's size and layout, these assisted the flows of water in carrying away sewage.

Some of the more powerful spells that Ahghairon bound into the sewers involved mass teleporting waste straight to the Rat Hills. These spells continued to be renewed over the years by members of the Watchful Order of Magists and Protectors.

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

Construction
The ceilings, floors, and walls all throughout the sewer system were made of masonry, often times with paving bricks. 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 were quite thick. Some were permanently set into the stone walls, while others could swing open on pivots. By the 14 century DR, many of these grates were suffering from rust.

One of the two oldest parts of the sewers was a large semicircular channel, which ran around the inland side of the spur of Mount Waterdeep that jutted out into the Castle Ward. Waste from the North Ward and Sea Ward drained through this channel. The other oldest structure was two trunk sewers, which drained waste from the Trades Ward and Southern Ward. Both structures emptied out into Deepwater Harbor.

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 a single  wide ledge on one of their sides, usually the more easterly or southerly side.

Primary passages were far more common in the northern parts of the city's sewers, while secondary passages were prevalent in the areas beneath the Dock Ward.

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. One of the oldest set of passages sat beneath Dock Ward and were known as the Smugglers' Run, since smugglers could navigate small boats through it.

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. This sewer passage paralleled the docks north of Sail Street, branched near Mirt's Mansion, and linked up to a junction room (SF48). The Grim Passage itself 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.
 * Fireplace Level: This complex of rooms within the Dungeon of the Crypt was connected to the midden of the Grinning Lion and a junction room in the sewers beneath it (SF31) by means of a secret staircase.
 * 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 were also a wide variety of fungi and oozes that lived in the sewers, with there being a small chance of an ooze crawling its 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. Such groups sometimes hired Cellarers to guide them through the sewers at the cost of 20 gold pieces a day, but such guides never carried weapons and would stick to only traveling the primary passages.

Explorers of the sewers risked exposure to sewer plagues. The waters were generally tainted with blinding sickness and any open wounds ran the risk of being contaminated with filth fever.

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, wererats, kobolds, and kuo-toa.

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, wererats, green slimes, brown molds, and yellow molds.
 * 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, yellow musk creepers and zombies, and magerippers.

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, covered by a stone hut. 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.  The ladder of this shaft was a  descent.
 * 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. Sometime between 1368 and 1372, the proprietor of the Grinning Lion installed a secret passage between this junction room and the stairs beneath his tavern's midden.
 * 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.
 * SF51: A surface shaft located in a cul-de-sac that opened off of Belnimbra's Street.
 * SF52: A surface shaft located in the westernmost dead-end of Quaff Alley. Opened into a junction room.
 * SF53: A surface shaft located on Soldier's Street, just east of the Bell Tower.
 * SF54: A surface shaft located at the intersection of alleyways north of the Three Pearls Nightclub.
 * SF55: A junction room without any surface shaft, located under the wide part of Candle Lane.
 * SF56: A surface shaft at the westernmost end of a dead-end alley that opened south off of Simples Street. Opened into a junction room.
 * SF57: A surface shaft located at the intersection of Burdag Lane and Tsarnen Alley.
 * SF58: A surface shaft located at the mouth of a dead-end alley, where it joined Quilley Alley between Nethpranter's Street and the Wide Way.
 * SF59: A surface shaft located at the western end of a dead-end forked alley, which opened east off of Rivon 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.
 * SF72: The lair of Xanathar, located directly beneath the Philosopher's Court.
 * SF73: North entrance into the Citadel of the Bloody Hand. Connected the secondary passage west of SF53 with the once-secret northern entrance. There was a guard station here, once used to defend Castle Waterdeep from subterranean attacks.
 * SF74: Southern entrance into the Citadel of the Bloody Hand. Connected the secondary passages running north and west of SF48 with the once-secret southern entrance.
 * SF75: A collapsed section of sewer floor and flooded storage vault of a forgotten merchant, used as a lair by the Savants of the Dark Tide.

Entrances into the sewers that were not labeled on the map included the following locations:
 * Dragon Tower: A wizard's tower in the Sea Ward that had a secret entrance to the sewers hidden in its first floor kitchen.
 * God Catcher: Sometime after 1385 DR this sunken, former Walking Statue in the Castle Ward had its leg hollowed out to create an access point to the sewers (see "History" for more information).
 * 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.
 * Lightning Targe: A newer adventuring club that had a rather mildewy tunnel connection to the sewers.
 * 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.
 * Thirsty Sailor: A tavern in the Dock Ward that had some kind of entrance into the Smugglers' Run section of the sewers in its back alley.

Groups of Interest

 * Cellarers' & Plumbers' Guild: Most members of this guild learned 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. They also possessed maps of the sewers, but they never sold them.
 * 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. All Watch captains possessed keys to the sewer access points of their assigned ward.
 * 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.
 * Cult of the Rat: A beast cult that worshiped Sneel, the lesser deity of rats, lived and operated in secrecy in the sewers throughout the 14 and 15 centuries. Many of its members were individuals who allowed themselves to be afflicted with the wererat form of lycanthropy. They often had offerings to Sneel in their warrens, meant to try and earn his favor.
 * 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, dating as far back as 1162 DR. As far back as this date, there existed three levels to the sewer system.

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 the archeaologist Wently Kelso.

In 1208 DR, in the month of Kythorn, some unauthorized construction was discovered on the second level of the sewers.

After securing a stronghold in 1262 DR (that would later be renamed the Citadel of the Bloody Handy), the Shadow Thieves constructed for it two links to the sewers of Waterdeep.

In 1280 DR, in the month of Mirtul, some trapped sewer gas was cleared from an area on the third sewer level. A year later, on the month of Kythorn, a cistern area was added to the second level of the sewers. And in 1292 DR, on the month of Tarsakh, flood control gates on the second level were repaired and additional ones were installed.

In 1298 DR, the Shadow Thieves were driven out of the city and the Lords of Waterdeep had the citadel's two passages to the sewers garrisoned by the City Guard. From then on they were occasionally employed by high-ranking occupants of Castle Waterdeep when a discreet exit was desired.

Some time in the late 1350's DR, on Mirtul 15, twelve tanystropheus eggs ordered by Phalantar's Philtres & Components hatched and escaped into the sewers via a garbage chute. That night a crew of Cellarers were attacked by the young dinosaurs while laying a large, heavy length of pipe. One member was killed, while two others were badly mauled. Frustrated by this, the guild offered a reward of 200 gold pieces for their capture (dead or alive), while Phalantar Orivan himself offered 500 gp for live specimens and 100 gp for dead ones. By the end of Uktar, it was assumed that any tanystropheuses not recovered were dead from the winter weather.

Around this decade, false and terribly inaccurate maps of the sewers were being sold by people trying to pass themselves off as Cellarers.

In 1355 DR, in the months of Ches and Tarsakh, flood control blocks were proposed for some areas of the upper sewer level.

In 1357 DR, a man from Luskan by the name of Neruudan set about making a smuggling ring in Waterdeep. To that end, he hired an evil mage to clear out the upper sewers. The mage put a giant crocodile in the sewers, with his quasit familiar riding upon its back and directing the beast, killing members of the Cellarers and Plumbers Guild until they began to refuse to do work. However, Neruudan was unaware of the sewers' use as a highway by locals and their wide selection of dangerous fauna, which eventually lead to the downfall of his plans.

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.

Also during this year, on Marpenoth 7 an adventuring band received orders from the Lords of Waterdeep to travel into the city's sewers to put an end to the ongoing plans of Xanathar. Before embarking into their depths the adventuring band was gifted by Khelben Arunsun with a partial map of the sewers and a copy of Wently Kelso's The World Beneath Waterdeep, which included several notes on the hazards and creatures they could expect to encounter. Secretly aided by another beholder, the adventurers managed to slay the crime lord and present his eye stalk to the Lords of Waterdeep, while the other beholder assumed the identity of Xanathar and took over his criminal organization.

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. Following this event, the guard station located near the northern entrance to the Citadel of the Bloody Hand became primarily concerned with guarding against the living spells that still remained after Halaster's Higharvestide.

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 army of Iakhovas there was one trio, hailing from the Swordsea Depths, who had joined in this assault for the sole purpose of using the chaos to sneak their way into the city's sewer system. 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. Also around this time, eyeballs and lurking stranglers roamed the sewers on behalf of Xanathar.

In 1385 DR, the Spellplague hit Toril and caused all of the Walking Statues of Waterdeep to become animated and wreak havoc across the city. The Blackstaff at the time, Tsarra Chaadren, turned the ground to mud underneath a statue known as the God Catcher. It sank partway into the ground, one of its legs penetrating a sewer line. Once the statues became immobile the God Catcher remained where it had sunken and was eventually converted into a tenement building, while its leg was hollowed out to create an access point to the sewer system.

Around In the late 15 century DR, a number of dwarves attempting to dig larger homes for themselves in Undercliff inadvertently breach Waterdeep's sewers in the process.

In, shortly after Mistshore was largely destroyed in a massive fire, Xanathar had some areas of the sewer network diverted in order to give his organization more space, which resulted in a large daily influx of sewage into Deepwater Harbor. Merfolk who lived nearby made attempts to clean the area, but were slaughtered by an undead eye of the deep under Xanathar's command. Eventually, Laeral Silverhand intervened &mdash; the meddlings of Xanathar were undone, the eye of the deep was slain, and harbor waters were revitalized.

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.
 * Some claimed that members of the Cellarers' & Plumbers' Guild could purposely cause the sewers to back up and overflow into certain buildings as an intimidation tactic.
 * The Cliffwatch Inn's cellars were rumored to have secret passages 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.