Detailed encounter, easily convertible into an adventure. Starts from investigating ambushes on the mountain pass and quickly escalated into a more twisted story about duergars, alhoons, and treasure vaults. Setting-agnostic (classic fantasy - best)

Part megadungeon, part underground expedition, Operation Unfathomable serves as both a one-shot adventure and a campaign framework. PCs are (optionally) drafted at swordpoint to recover the Nul Rod, a priceless artifact that was recently lost in a local prince's foolhardy attempt to destroy the Chaos Gods of the Underworld. The PCs have been drafted as an expendable set of pawns to venture into the vast and bewildering Underworld and retrieve the Nul Rod. With the Underworld's innumerable beasties being on high alert after the prince's expedition, the PCs must sneak through the incredibly dangerous Underworld. Fighting is not as important as stealth, fast-talking, and running away rapidly. This is the expansion from Sholtis's original Operation Unfathomable, released in Knockspell #5 (2011).

A strange journey through a living cavern. A request for help to rescue a mining crew leads a group of adventurers into a cave that has seemingly come to life, gripped by a melancholy wave of sadness and memory. In dark caverns where mushrooms walk, vines dance, walls watch, and stones speak, will your band of adventurers become heroes? Or will they be lost within the Mines of Memory? Mines of Memory is a short, 2-3 hour adventure for characters of levels 1-3. It is a delve into a cavern system that has become a Psychic Resonance environment, awakening the caves themselves. PCs will enter to rescue the miners, find the source of the mine’s awakening, and bring peace to a noble creature trapped in its own nightmare.

Hunt for a Legendary Treasure! Deep beneath a peaceful valley lies the vault of the legendary drow adventurer Larin Karr. Rumor has it Larin Karr has gone, but his vast treasure acquired from years of plundering hordes in the Underdark still remains. Can you find and loot the impenetrable vault? The Vault of Larin Karr details Quail Valley, its residents and monsters, and the twisting tunnels of the Underdark that stretch beneath it. The Vault of Larin Karr takes PCs from 4th to 9th level, during which time they fight dragons, find a missing statue for a band of renegade elves, save the village of Pembrose from scheming hobgoblins, and explore the Underdark and its many dungeons - including the legendary Vault itself! Contains new monsters and magic items! 2003 ENnie Award Silver Winner: Best Adventure

"Imperial Ghoul Outpost" is an iron ghoul lair suitable for four or five 10th-level characters. This adventure can be completed in a single session. When a clan of duergar prospectors unearthed caverns not on the their maps, they were particularly excited about a strange new iron orc they found there. not long after mining began, undead horrors emerged to attack the dwarves. Only one duergar escaped, his mind shattered by the experience. The Ghoul Imperium continues to explore the area, and it has its own plans for the newly discovered one.

The most deadly dungeon ever devised! High-level characters brave the unexplored corridors of Deepearth to confront perhaps the most feared adversary in the AD&D game. The second chapter of the Bloodstone Pass saga follows the conclusion of the desperate war against the bandit army. A cold and bitter winter drives the villagers to the edge of starvation, and numerous horrors strike the town of Bloodstone Pass. Join the adventure as the heroes explore the depths of the ancient bloostone mines, now inhabited by fearsome demons. There they hope to uncover the fantastic treasures rumored to exist in the unknown darkness. But deep within the mines, all is not what it seems.... This module uses the new rules from the Dungeoneer's Survival Guide and Wilderness Survival Guide. The adventure also includes optional BATTLESYSTEM scenarios fought entirely underground. These supplementary products are not required to play the adventure, however. TSR 9168

The Underdark is a subterranean wonderland, a vast and twisted labyrinth where fear reigns. It is the home of horrific monsters that have never seen the light of day. It is here that the dark elf Gromph Baenre, Archmage of Menzoberranzan, casts a foul spell meant to ignite a magical energy that suffuses the Underdark and tears open portals to the demonic Abyss. What steps through surprises even him, and from that moment on, the insanity that pervades the Underdark escalates and threatens to shake the Forgotten Realms to its foundations. Stop the madness before it consumes you! Note for DMs: This adventure is not for the faint of hearted, to run or to play. The module starts with 10 NPCs traveling with the party through the grueling Underdark. This number can grow. The encounters within the book are often incredibly deadly for the characters that would be going through it. This is because the module expects them to run or talk their way through the events, or, in some cases, the module expects them to lose. If your players aren't the kind of party to run, talk, or surrender, do not get this adventure. The module almost requires that you use milestone leveling because the experience provided does not commonly get players to the levels they should be once they get to certain milestones in the story (7th when they leave the underdark, 15th when they face the demon lords.) Good luck and happy questing.

The kuo-toa are a piscine race with a psychic affliction that makes them behave erratically and invent gods when feeling threatened. That same affliction gives them the power to bring those gods to life. Blibdoolpoolp is the most widely worshipped, and thus most powerful, of their gods. Blibdoolpoolp views the kuo-toa as her children despite having been born after them. Like all good mothers, she nurtures and protects. One of her chief concerns is understanding the kuo-toa’s psychic affliction, which causes them to undermine themselves whenever they strive for greatness. She discovers that a corrupted elder brain deep in the Underdark has a connection to the race; though the connection gives them psychic powers, it also turns them into powerless thralls, explaining their self destructive behaviors. Constrained by the same leash on her children, Blibdoolpoolp seeks adventurers to destroy the elder brain. Its death would free the kuo-toa, but potentially at great cost: if the kuo-toa lose their powers, will Blibdoolpoolp die?

Of all the inhospitable domains in the RAVENLOFT@ campaign world, Bluetspur is the cruelest and most gruesome. Nothing grows in the endless night, and lightning periodically falls like rain. The only place to escape those storms is inside the mind flayers' complex under Mt. Makab, but that is the last place where any sane person would want to go. The High Master Illithid has been hatching black plots by hatching vampiric mind flayers in his laboratories! His prodigies are horribly insane, but if he can complete his plans, he will achieve a new level of dark immortality. A pair of heroes has stolen the key to his success, but they have paid a heavy price for their bravery and are in desperate need of aid unlooked for. Meanwhile, the Lord of the Realm watches over the proceedings and plays havoc with the wits of both sides, sapping strength and will with all-powerful thoughts of darkness. A party of adventurers will need all of their skills to escape this black domain without the loss of life, power, or sanity! Enter now the perpetual twilight realm of Bluetspur, home to mind flayers, a land of relentless nightmares. There's no rest for the wicked or the good in this domain. Once caught within the borders of this desolate land, the characters must complete their mission without delay or lose their minds and become slaves of the Lord of Bluetspur. TSR 9264, from 1992

TENTACLES. WHY DID IT HAVE TO BE TENTACLES? A colony of deep gnomes have had their main water source taken over by a group of kuo-toa, but are the fishy folk really the ones to blame for leaving the gem-loving svirfneblin thirsty?… This adventure was originally made for a West Marches campaign, but is designed to easily fit into any standard fantasy setting. There are many areas to insert plot hooks for your own world or campaign. A 4-hour adventure for 5th-7th level characters by ALAN TUCKER

The Ghost Tribe of Orcs were driven from their home under Wyvern Tor by some terrible evil. They marched to Phandalin and attacked, only to be defeated. Now the heroes will go beneath Wyvern Tor to discover the terror that chased out the orcs and perhaps find the source of the orc’ssardonyx. Journey to Beneath Wyvern Tor is the third of four parts in the After Lost Mine series. It will play out the journey to the orc’s former cave settlement and then into the darkness beneath. Part IV will have the party deal with the terror from the Underdark that drove out the orcs.

In Prisoners of the Drow, a band of adventurers storm a drow outpost, confront the drow mage in charge of it, and rescue prisoners held within. The heroes must bypass traps and devious defenses to reach their goal and accomplish their mission. The adventure is designed for a party of five adventurers between levels nine and twelve. It features: Encounters by Level - Varying types and quantities of creatures are suggested based on the party's actual level, allowing each encounter to present the appropriate challenge to the party. Encounter Notes - Suggestions for how to run combats are provided for game masters who place an emphasis on engaging, tactical battles. Inciting Action - Suggestions for ways to present the adventure to players are provided. Ease of Use - The format and style of the document allows the game master to find information quickly while running the game at the table. Detailed Maps - What's an adventure without maps? Not much else to say here. This adventure is designed as the first in a two-part series. The second adventure Into the City of Spiders takes the adventurers into a drow compound far from the surface. https://www.drivethrurpg.com/product/247674/Into-the-City-of-Spiders

This adventure is written with the intent that it takes place in the subterranean world called the Underdark in the world of Forgotten Realms, although it may be placed in other settings. Within the Underdark, Cyrog's lair can be placed anywhere though it is stated to be thousands of miles east of Gravenhollow. If you are running Out of the Abyss, you may want to have your players see the vision Cyrog Lives! Hail Orcus! (OOTA, 158). Additionally, it is recommended that this adventure be used for a party of 4 to 6 players, level 9 to 12. While merely hinted at through visions in Out of the Abyss, Orcus is roaming the Underdark unchallenged with an army of mind flayers at his disposal. Cyrog, the elder brain of a mind flayer colony in the Underdark has died. The demon lord Orcus has reanimated and taken control of it. The hive of mind flayers is now bent to Orcus's will through Cyrog as he strives to make all life in the multiverse into a vast undead horde under his control. The adventurers are contacted by a patron who gives them a special item (such as brain worms) to suppress their brain waves and make it possible to infiltrate the Cyrog's Lair without immediate detection. The adventurers must defeat or otherwise subdue mind flayers and a few guards, override the elder brain's mechanical defense system, and slay Cyrog.

The Shattered Circle is an AD&D® adventure for four to six player characters of 1st to 3rd level. For many ages, the standing stones known as the Circle of Cahervaniel have stood on a grassy hilltop, unremarkable and unmenacing, but something has changed. A powerful artifact deep within the earth has been uncovered, and its evil power has corrupted the recent inhabitants of a dungeon complex. The chitine live within, a cross between humans and spiders created by the drow, but trying to live a quiet existence. The evil Foundingstone has corrupted some of the chitine, and split their society in two, bringing them to conflict. Adventurers who navigate the chitine factions and dangerous dungeon will need to end the threat of the Foundingstone and the solve the mystery of the strange dark unicorn Mizar that has appeared recently around the stones. Interestingly, one of the unique magic items in this adventure, Icerazor - is said to have grown from a shard of Frostrazor, a sword that appears in a famous later adventure - Return to White Plume Mountain. There is a brief mention of Suloise, so it can be considered a Greyhawk adventure, but clearly states it can be placed anywhere.

Having put down a rising of giants, it was discovered that the motivating force behind their depredations was that of long-forgotten evil - the Dark Elves. Determined to seek out these creatures, a body of doughty adventurers mounted an expedition to learn the strength of the Drow and bring retribution to them (DUNGEON MODULE D1, DESCENT INTO THE DEPTHS OF THE EARTH). This module contains background information, a large-scale referee's map with a matching partial map for players, referee's notes, special exploration and encounter pieces, a large map detailing a temple complex area, encounter and map matrix keys, and an additional section pertaining to a pair of unique new creatures for use with this module and the game as a whole. A complete setting for play of ADVANCED DUNGEONS & DRAGONS is contained herein. This module can be played alone, as the second part of a series of three modules (with DESCENT INTO THE DEPTHS OF THE EARTH, D1, and VAULT OF THE DROW, D3), or as the fourth part of a continuing scenario (DUNGEON MODULES G1, G2, G3, D1, D2, D3, and Q1, QUEEN OF THE DEMONWEB PITS). TSR 9020, From 1978

Tales of Lady Sepha Lekore are known throughout the lands. Now she’s gone missing and her father Lord Lekore is offering a reward to anyone that can find her. With promises of a tidy sum, the adventuring party can investigate the last place she was seen to try and locate her. What they find will take them into the Underdark lair of a drow noblewoman with her eloped love, the young Lady Lekore.

Part 3 of the Shackled City Adventure Path "Wherein a tribe of the Sea Mother's children suffer for sparing the life of a mad prisoner they probably should have eaten." Synopsis: The adventure begins with an Umber Hulk attack in the middle of the city. The fame gained by assisting during the attack allows them to gain the notice of a representative of Davked Splintershield. The group is asked to rescue Zenith Splintershield from a Kuo-Toan temple in the Underdark. But to find it, they have to visit Crazy Jared to locate an entrance to it. Upon journeying to Crazy Jared's, they fight Hookface's offspring. After more travelling, they are able to descend into the Underdark. Once they find the Kuo-Toan temple, they must fight through many hard challenges, only to realize that Zenith is not a prisoner, but instead is a prophet. Zenith does not go willingly, and so must be captured. Pgs. 28-61

This 4 hour adventure for 3rd level characters begins in a prison cell where the adventurers must figure out a way to escape, acquire weapons and armor to defend themselves more effectively, and most importantly, escape a repurposed dwarven forge that has been appropriated by a fire giant who uses slave labor and even a captured red dragon wyrmling to smelt ore and forge an arsenal under the volcano Mt. Hotenow.

The final confrontation with the giant, King Snurre, and the entry of mighty adventurers into the caverns under his stronghold (DUNGEON MODULE G3, HALL OF THE FIRE GIANT KING) discovered the Dark Elves, the Drow, had instigated the giant alliance and its warfare upon mankind and its allied races. This module contains background information, a large-scale referee's map with a matching partial map for players, referee's notes, special exploration and encounter pieces, a large map detailing a cavern area, encounter and map matrix keys, and an additional section pertaining to a unique new creature for use with this module and the game as a whole. A complete setting for play of ADVANCED DUNGEONS & DRAGONS is contained herein. This module can be played alone, as the first part of a series of three modules (with SHRINE OF THE KUO-TOA, D2, and VAULT OF THE DROW, D3), or as the fourth part of a continuing series of modules which form a special progressive campaign scenario (DUNGEON MODULES G1, G2, G3, D1, D2, D3, and Q1, (QUEEN OF THE DEMONWEB PITS). TSR 9019

In this small 20 page adventure module, centered around an archaeological dig, revisit Bull Creek and find out the secret behind what really lies in the hero Vertrixx Mazilaxx's sarcophagus. To do so, you'll have to meet up with master archaeologist Geranimus to delve deep into the ground. On the surface, politics boil and tensions between species are high. Below, secrets are to be uncovered. Can your party find the truth? Find out in Old Bones. Old Bones- a 5e SRD adventure for levels 4, 6 and 8. In James Grammaticus' Dungeon Short series, James explores fantasy worlds and settings in short bite-sized one or two shot adventures that be used on their own, can spring off into a larger campaign, or can be used as a side-adventure in a campaign.