Return to Undermountain
Return to Undermountain Introduction
By Matthew Sernett

Undermountain? Ah, yes. A great place to have fun, the most famous battlefield in which to earn a reputation as a veteran adventurer -- and the largest known mass grave in Faerūn today.

-- Elminster of Shadowdale

Undermountain, that seemingly endless dungeon beneath Waterdeep -- mentioned in countless Forgotten Realms products, detailed in two boxed sets and several adventures, and so vast that such efforts barely scratched the surface of its many miles of corridors and acres of rooms -- remains one of the most recognizable locations in Faerūn. Often called the "deepest dungeon of them all," Undermountain has tempted countless adventurers to delve into its depths. Some return with tales of its horrors. Most are never seen again. Yet enough of those few who return come back with astounding wealth to entice others to follow suit and take the chance that the halls beneath the mountain become their tomb.

This article series details some of the rooms and halls of Undermountain so that you can use them in your game. As with the many Undermountain products of the past, this series of articles cannot hope to detail every room and corridor of the vast dungeon beneath Waterdeep. Instead, it will detail individual rooms and encounters that you can use when you run adventurers through Undermountain or any dungeon of your own devising.

TSR published The Ruins of Undermountain, the original boxed set describing the first three levels, in 1991. A few things have changed since then. Fans of the old dungeon description will find some new encounters, recognize some old favorites, and be surprised by some new twists. For those new to Undermountain, this introduction acts as a primer, telling you what you need to know to imperil PCs' lives in the Forgotten Realms setting's most famous dungeon.

How to Use Undermountain

This articles series presents the map of the first level of Undermountain and describes a few rooms within it each month. These dungeon rooms share Undermountain as a linking theme, but you can easily take them out of this context and place them into any adventure of your making. If you want to use Undermountain as a setting for your PCs' adventures beneath Waterdeep, don't wait for all the articles before you get started. You can use the map and the first few rooms as a starting point for adventures you devise, and if a future room description contradicts your version, you can incorporate the room in another part of the dungeon or have the room change to fit the new description, presenting a surprise to your players.

A Short History of Undermountain

Over a thousand years ago, the wizard Halaster Blackcloak whirled to the base of Mount Waterdeep, called there from a distant country by chance or providence. Some say he hailed from the Cradlelands, the nearly forgotten empire that spread humanity across Faerūn and Kara-Tur from what is now the Plains of Purple Dust, a wasteland created by conflict with the gods. Whatever his origins, scholars record that Halaster brought with him the Seven, as his apprentices are known, and with their help and his power, Halaster summoned beings from other planes to build himself a wizard's tower. Halaster ringed his tower with a great wall set with lesser towers for each of his apprentices, and he created fields and farms to be worked by his apprentices and their servants.

For a time, it seemed a good life for the Seven, but as the days wore on, they saw less and less of their dread master. Halaster continued to use fell creatures from other planes for construction beneath his tower, and he kept his dealings with them and the nature of the tunnels from the Seven. At length, Halaster's tunneling broke into the Underhalls, a complex of tunnels built by dwarves around a mithral mine beneath Mount Waterdeep. The dwarves who built the dungeons, the Melairkyn clan, had long ago been killed or dispersed, replaced by oft-times warring duergar and drow. Halaster began a crusade against both races, participating in wild hunts through the tunnels with allies called from the Outer Planes. The duergar stubbornly remained until the mithral was largely mined out, but then they left the drow to fight Halaster and his minions alone. Halaster captured or killed the remaining dark elves, entrapping their souls for dark magic or twisting their bodies and enslaving their minds. When the last of the drow were defeated, Halaster Blackcloak tunneled on, ever downward, continuing his strange obsession with delving beneath the mountain.

Finally, when Halaster was absent for more than a year, some of his apprentices ventured into his tower in search of the great wizard. They found traps, monsters, and tantalizing hints about power beneath the earth. Individually they plumbed the depths of the dungeons, encountering evermore-deadly traps and more powerful foes. For their efforts, they were rewarded with riches and magic. When the Seven were reduced to five, Halaster appeared to his students and explained that he had built the tunnels to guard his experiments and treasures. He enlisted their aid to make his dungeons even more secure.

What happened after that is unclear, but only one apprentice is known to have left Undermountain, and she fled the area, never to return. Halaster continued to live beneath the mountain, using it as a base from which he traveled to other planes and distant lands, entrapping strange creatures and bringing them back to live as prisoners or guardians in his home. In time, Halaster sought out magic to extend his life, and some say that it was these spells and items that finally drove Halaster beyond all reason. While before he had been obsessed and deranged, his quest for immortality seemed to drive him truly mad.

While Halaster quested on other planes and sequestered himself in his tunnels, his tower fell into ruin. When Halaster was yet active in the outside world, his home was considered an accursed place, so settlers in the area largely left the crumbling tower alone. In time, the city now known as Waterdeep came to huddle against the mountain and reach down to the harbor. As the city sprawled outward, it reached and encompassed the ruins of Halaster's home. Undermountain was known to these early settlers, and they often punished criminals by sending them into its depths. So it was for many years until an adventurer named Durnan delved into the depths beneath the tower and returned, laden with riches, to tell the tale. Durnan demolished the last remnants of Halaster's above-ground abode and built an inn over the well he had used to descend into the depths. He called his inn the Yawning Portal, and Durnan works there to this day, serving patrons and inviting the brave or the foolish to try their hands at the halls of Undermountain.

Reasons to Enter Undermountain

If riches and power aren't enough to entice your players' PCs to try their luck in Undermountain, there exist countless other options to get them involved. Presented below are a few ideas for how to get their adventures beneath Waterdeep started.

  • A nobleman ventured into Undermountain and has been gone for a week. Divinations revealed he is alive and held captive in the dungeon complex, but attempts to divine his exact location have failed. His house offers a tremendous reward for someone to rescue him.

  • One of the PCs' long-time foes ventures into Undermountain along with a captive, magic item, or holy relic important to the PCs. Their only hope of regaining what they've lost is to follow.

  • If the PCs rack up a great debt, someone might call in that debt and offer Undermountain as a means of quickly gaining enough for payment.

  • Other adventurers challenge the PCs to enter Undermountain with them, betting their takings from the dunegons against the PCs' with the group who amassed the most taking all. If the PCs refuse, the other adventurers call them cowards, and their bard makes up some catchy tunes about the party's lack of courage.

  • If the PCs run into trouble with the law or with a criminal organization, they might be sent into Undermountain as punishment. Capital punishments are sometimes commuted to just such a penalty.

Ways In and Out

Many ways lead into Undermountain and few ways lead out. Many seeming exits just lead farther into the maze, and many traps dump their victims in deeper levels of the dungeon. A future article might detail some of the many exits and entrances to Faerūn's largest mass grave, but this series assumes the PCs enter and exit by one: the well at the Yawning Portal Inn.

The Yawning Portal

The Yawning Portal, famous for holding the entrance to Undermountain, stands in Waterdeep on Rainrun Street in the upper part of the Dock Ward. It's a must-see location for many visitors to the great city, and many adventurers use it as their starting point and refuge during their dungeon plumbing.

Built on the site of Halaster's tower, the Yawning Portal is a rambling structure strewn with blue tapestries. Food at the inn is decent and prices for room and board are fair. Durnan (NG male Ftr18) built the Yawning Portal with wealth taken from the Undermountain, and he has run the inn since his retirement from adventuring more than seventy years ago. Now approaching a hundred years of age, the white-haired Durnan is nevertheless a powerful presence behind the bar, and many consider him an institution in Waterdeep. With muscles like catapult shots and a greatsword hung among the racks of mugs and bottles, few make trouble in the inn, and those who do quickly come to regret it. The local toughs and bravos know better than to set foot in the Yawning Portal, and newcomers to the inn receive a friendly welcome from other patrons along with an admonishment about fighting or casting spells. Durnan asks those who do come to conflict to leave the inn, ejecting them if they refuse. A few off-duty city guards are usually in the taproom, and they call on their fellows to arrest any brawlers, whether inside or outside. As a result of Durnan's influence and the attraction of the entrance to the dungeon, having dinner or a drink at the Yawning Portal remains a relatively safe and entertaining way to spend time, and many local laborers and merchants rub shoulders with the exotic foreigners and adventurers drawn to the place.

The centerpiece of the taproom is a wide well with a low wall. This is the "yawning portal" and the entrance to Undermountain. The well is surrounded by everburning torches, and a large winch-and-pulley construction hangs a rope over a 140-foot drop into the dungeon. Entrance to Undermountain costs 1 gp. Durnan happily lowers any paying patron into the well by means of the winch and a long length of silk rope. Durnan doesn't like lowering more than one person on the rope at a time, although he'll make exceptions for Small characters and exceptionally light individuals. If someone insists on being lowered with more weight than Durnan thinks the rope can hold, the innkeeper asks that the party pay for a replacement for the rope in advance, and should it break on the way down, Durnan hollers an "I told you so" to the falling adventurer -- much to the amusement of his patrons. Those who make use of the well without paying earn Durnan's ire, and he refuses to raise them out of the well without having them first tie their wealth and gear -- everything but underclothes -- to the rope. Durnan then keeps the wealth and holds the gear and items until the adventurer can afford to buy them back at a fair price or pay 1,000 gp, whichever is less.

If an adventurer returns to the well and wants to come back up, he must have 1 gp to pay Durnan. Those who can't pay must give Durnan their gear, paying Durnan 500 gp or the cost of their gear before he returns the items. If someone refuses Durnan's terms or attempts to leave without paying, Durnan either leaves them at the bottom of the well or forcibly puts them back down there. The 140-foot drop convinces most folk that embarrassment and poverty is the preferable option.

Durnan provides other services to adventurers. In addition to providing food and libation, he rents rooms and storage lockers, and he keeps some dungeoneering essentials on hand to sell to those who might have forgotten something in their preparations. Use the prices for equipment, edibles, and inn stays as provided in the Player's Handbook. Durnan charges 5 gp a day for use of a storage locker, and he requires payment up front. He sells the items stored within if a person doesn't return to take them. This might seem steep, but few safer places exist within the city to store wealth and goods than with Durnan. Durnan also sells healing potions provided to him through the temple of Tymora in the city. He charges the price in the Dungeon Master's Guide since he buys them in bulk at a discount. Durnan doesn't provide other healing or help to returning adventurers, but he'll send a runner with a message to one of the temples for free. (He considers such a small service to be paid for by the PCs' entrance fee and the entertainment they provide to his patrons simply by choosing to delve into the dungeons.)

When adventurers pay to enter the well, patrons cheer, share rounds of drinks, and generally give the heroes a grand going-away party. For those not distracted by the celebration, the scene might seem a bit grisly as customers at the inn and those working there openly bet on whether or not the adventurers will return, in what state they'll return, and how many might come back. Adventurers are not allowed to participate in this betting.

The Powers of Halaster

Halaster (male human Wiz25/Acm5, detailed in the Forgotten Realms Campaign Setting and updated in Epic Level Handbook) still roams the halls of Undermountain and views them from a secret base unreachable from the dungeon's tunnels. In past products, Halaster's influence provided an explanation for traps resetting, monsters being replaced, and to obstruct the use of certain types of magic. You can use Halaster's powers in a similar manner, but such things can be frustrating to players, so employ such tactics with caution.

These articles assume that Halaster's influence is felt in just one manner: a teleport cage (see City of Splendors: Waterdeep, to be released in July, for a spell description) that encompasses all of Undermountain. When a conjuration (teleportation) spell is cast within Undermountain, the spell transports all affected creatures and objects to another random location within Undermountain. When a caster outside Undermountain attempts to teleport into it, the effect redirects their destination to another random location reachable by the spell. For example, if a 9th-level wizard in Waterdeep attempted to teleport into the depths of Undermountain, the teleport cage would cause him to appear at another random location within 900 miles of the place where he cast the spell. This effect is well known, and Durnan warns adventurers of it before winching them down.

Here are some other possibilities for Halaster's influence that might make adventures in Undermountain unique.

  • Spells that alter the dungeon, such as passwall or stoneshape, fail or go wild.

  • Divination magic of various types, such as scrying and magic that locates objects or creatures, fails or goes wild.

  • The whole dungeon might radiate powerful obscuring magic, making detect magic useless as a means of discovering magic traps.

  • Traps reset after a designated a period of time.

  • Portals open at random, sometimes depositing monsters in rooms thought to be empty.

Dungeon Features

This section describes assumptions about the features of Undermountain. See the Undermountain Cheat Sheet sidebar for statistics you might like to keep handy when running adventurers through one of the rooms described in this series of articles.

Map Squares: Note that squares on the large Undermountain map represent 10-foot squares, just as they did in the original Ruins of Undermountain boxed set. In the maps of each room that accompany the articles, squares represent normal 5-foot squares.

Climate: The temperature in the dungeons tends to be a little chilly, but dungeon delvers don't require more than typical adventuring garb. Parts of the dungeon are dank and moldy while others are dry and dusty. Some parts of Undermountain vary greatly from the norm, and in such cases, the room description will note this. Many sources of fresh air lead into the various levels of Undermountain, and unless otherwise noted, the air in the dungeons is clean apart from occasional dustiness or dampness.

Ceilings: Unless otherwise noted, ceilings in rooms are 10 feet above the floor. Although once constructed of smooth stone, most ceilings bear the cracks and pock mocks from centuries of age and countless battles. Unless otherwise noted, PCs can climb ceilings (hanging from hands) with a DC 25 climb check.

Floors: Most floors in Undermountain rooms consist of relatively smooth stone or flagstones. Neither floor type requires special rules for movement.

Floors in caverns should be considered hewn stone floors. A character running or charging on a hewn stone floor must make a DC 10 Balance check or be unable to run or charge (the character can still act normally).

Other floor types exist in Undermountain, and when necessary, their description will appear in the description of a room. For more information on floors, see page 60 of the Dungeon Master's Guide.

Walls: Halaster and the dwarves and drow before him constructed Undermountain of walls of superior masonry. Cavern walls are typically unworked. Both have a Climb DC of 20, 15 hit points per inch of thickness, and a hardness of 8.

Thin walls between rooms are 1 foot thick and have 90 hit points (half normal) because they lack the support of bedrock behind them.

Doors: Unless otherwise noted, doors in Undermountain are 4 inches thick, 5 feet wide, and made of stone. They sit and hang on pins on one side, usually the left side if one pushes the door open. Doors open into rooms from hallways, and into smaller rooms from larger ones, as a rule of thumb.

Stone doors have hardness 8, 60 hit points, and a break DC of 28 whether stuck or locked. All doors have built-in good locks (DC 30 Open Lock check to lock or unlock), but keys are largely missing, and locks are often broken. Unless other wise noted, doors are not locked or barred.

For more information about dungeon doors, see page 60 of the Dungeon Master's Guide. For more information about locks, see page 61.

Doors line up with a 5-foot square even though the main Undermountain map indicates they would straddle a line between squares.

Undermountain Cheat Sheet

Here are some statistics you might find handy as you run the encounters described in these articles.

Door (Stone): 60 hp (hardness 8); Break DC 28 (stuck or locked).

Secret Door (Stone): Search DC 20; 60 hp (hardness 8); Break DC 28 (stuck or locked).

Lock (Good): 30 hp (hardness 15); Open Lock DC 30. Note that locks built into dungeon doors cannot be attacked separately from the door.

Floor (Room): No special rules unless otherwise noted.

Floor (Cavern): DC 10 Balance check to charge or run.

Ceiling (Room): DC 25 Climb check.

Ceiling (Cavern): DC 25 Climb check; DC increases by +5 if surface is slippery.

Wall (Room): Hit points vary based on thickness (hardness 8); Climb DC 20. If the wall is a thin wall (1 foot thick) between rooms: 90 hp (hardness 8); Break 35, Climb DC 20.

Wall (Cavern): Hit points vary based on thickness (hardness 8); Climb DC 20.

Secret Doors: In general, secret doors consist of stone made to blend in with the surrounding walls. The typical secret door can be found with a DC 20 Search check, and it might or might not have a lock or even be opened from the side the PCs stand on. Remember that dwarves receive a free Search check to note unusual stonework, and elves get a free Search check to find secret or concealed doors.

Secret doors line up with a 5-foot square even though the main Undermountain map indicates they would straddle a line between squares.

Light and Darkness: Most of Undermountain remains unlit by any light source, but some rooms and halls might be lit by ancient magic or recent inhabitants. Room descriptions assume the PCs can see about 60 feet in darkness, so be sure to modify your description of the room if the PCs can see a shorter or farther distance in the dark. Also, recall that darkvision is in black and white.

Listen Checks: Remember that PCs passing near a door, secret door, or hall to a room with some activity in it might have an opportunity to hear what's happening on the other side. Similarly, creatures in distant rooms or passages have a chance to hear the PCs. See page 78 of the Player's Handbook for modifiers to Listen checks.

Spot Checks: Spot checks function normally in Undermountain, but remember that PCs can see only as far as their light sources reveal or their darkvision allows.

Random Encounters: A future article might detail random encounters particular to Undermountain, but for now, use the rules presented in the Dungeon Master's Guide on page 78. You can roll for a random encounter as often as you like, but keep in mind the party's condition and how the number of random encounters can affect how populated the dungeon seems to be.

Telportation: Conjuration (teleportation) spells transport all affected creatures and objects to another random location within Undermountain. When a caster outside Undermountain attempts to teleport into it, the effect redirects their destination to another random location reachable by the spell.

Traps: Traps of endless variety litter Undermountain's halls and rooms. Some traps exist merely to move dungeon delvers deeper into the dungeon or to get them lost. A future article might detail traps in Undermountain; for now, use the traps described in the Dungeon Master's Guide. When using traps, keep in mind their effect on the pace of the game; one hidden pit or arrow trap can cause the PCs to slow to a crawl as they check every step for hidden danger.

The Map

This poster map of the Ruins of Undermountain measures approximately 30"x22" and can be printed on one sheet of paper on a large-format printer or as individual 8.5"x11" sheets that you assemble. Wizards of the Coast, Inc. grants permission to use these images for personal use only.

Piece 1 Piece 2 Piece 3
Piece 4 Piece 5 Piece 6
Piece 7 Piece 8 Piece 9

Poster Map Instructions

The full-sized map of Ruins of Undermountain is approximately 32"x20" and is available in two formats.

30"x22" Format

This is one large file for printing to a large-format printer. It can also be used by programs that are capable of "tile printing" to break the map up into sizes that are appropriate for your situation.

8.5"x11" Format

This format has the single large map broken into nine 8.5"x11" sections for printing on a typical home printer, then assembling into the large poster size. This visual guide shows you which image represents which area of the map.

Future Articles

In addition to dungeon rooms and encounters, future articles might detail random encounters, traps, and dungeon dressings particular to Undermountain. For now, use Tables 3-18 through 3-21 beginning on page 78 of the Dungeon Master's Guide.

Better Adventures in Undermountain

Several products will make your adventures in Undermountain more fun and more detailed. Check out the following books for excellent ideas and great inspiration to add depth and detail to your PCs' dungeon delvings.

Forgotten Realms Campaign Setting: In addition to describing Waterdeep and the surrounding area, this book contains NPC statistics for Halaster and a few other noteworthy characters who might be met in Undermountain.

Epic Level Handbook: This book contains updated statistics for Halaster Blackcloak.

City of Splendors: Waterdeep: To be published in July, City of Splendors: Waterdeep details the city above Undermountain and describes the history of Undermountain and surrounding area in great detail. It's the perfect resource for a campaign in the great dungeon, and using it is an excellent way to have both city adventures and dungeon crawls at your fingertips.

Underdark:Underdark describes the inhabitants that dwell in the Underdark near Undermountain as well as giving great descriptions and advice for spelunking adventures.

Dungeon Master's Guide II: Chapters in this book include advice about running a game and designing adventures. Ready-made game elements include instant traps, pregenerated locations, and treasures.

Stronghold Builder's Guidebook: Although not designed for the revised edition of the game, the Stronghold Builder's Guidebook offers tons of great inspiration for dungeon design, from magical locations to magic augmentations on walls and floors that would send shivers down any adventurer's spine.

Lords of Darkness: Lords of Darkness presents many different factions, large and small, that could be antagonists in the PCs adventures in Undermountain. Whether you want the PCs to meet slavers or assassins, a thieves' guild or a cabal of necromancers, Lords of Darkness offers many tantalizing options.

Using Undermountain with Other Campaign Settings

You can use the rooms described in these articles in dungeons of your own devising, but you can also adapt all of Undermountain for use in your campaign, whether or not you run a game in the Forgotten Realms.

Eberron: Undermountain could be part of the depths of Sharn, or it could be a complex on the continent of Xen'drik. In Sharn, the wide scope of the dungeon means that it would have to be part of the deepest foundations of the city. In Xen'drik, you could raise the ceilings in Undermountain to 20 or 30 feet high and make the halls the work of giants and later expansions by drow. Sharn: City of Towers is an excellent resource for using Undermountain with Sharn.

Greyhawk: Countless locations exist that could host the halls of Undermountain. Perhaps the Undermountain map represents a lost level of the dungeons of Castle Greyhawk, or maybe Maure Castle has depths beneath the known levels.

Article Reference Map

About the Author

Once editor-in-chief of Dragon Magazine and now a game designer at Wizards of the Coast, Matthew Sernett wrote in a Dragon editorial that there's nothing in D&D he likes better than when the adventurers flee through the dungeon, running pell-mell through traps and past monsters because what chases them is worse. When he wrote that, Matthew was thinking about Undermountain.


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