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Deep Horizon (2001) is a 32-page adventure module written for Dungeons & Dragons 3rd edition by Skip Williams. It is intended for 13th-level characters.

It is the sixth work in a series of eight linked modules unofficially referred to as the Sunless Citadel adventure path. It consists of The Sunless Citadel (2000), The Forge of Fury (2000), The Speaker in Dreams (2001), The Standing Stone (2001), Heart of Nightfang Spire (2001), Deep Horizon (2001), Lord of the Iron Fortress (2002), and Bastion of Broken Souls (2002).

Spoiler alert: The following article contains spoilers for a Dungeons & Dragons product.



Centuries ago, the desmodus—bat-like humanoids inhabiting the Underdark—fought the drow in a war which threatened to destroy them. They sealed off their home caverns by re-routing a lava flow, destroying the drow city in the process. Nearly everyone assumed that the entire desmodu race had been destroyed.

Three months ago, an earthquake re-opened a path to the desmodus' domain, unveiled the lost drow city, and sparked conflict between the desmodus and their former trading partner, a colony of salamanders. The salamanders have struck an alliance with beholders who have taken up occupancy in the drow city. This in turn has led to political conflict within desmodu society as differing political factions disagree over the best way to handle the new threat.


The player characters descend into the Underdark and reach the ruins of a drow city, now occupied by beholders who have taken desmodu slaves. The desmodus lead them to an enclave of their people, leading to a murder investigation. Next, they lead an attack on a lair of salamanders. Alogn the way, they encounter rival factions of desmodu, each with their own agenda.

Development and release

Deep Horizon was written by Skip Williams, with art by Brom and David Roach.

The module was previewed at Gen Con 2001, held from August 2-5 of that year.[1].

It was released as a 32-page paperback in November 2001, for the price of US$9.95, or $13.95 Canadian.[2] It appeared under two product codes: WTC11855, and 886670000.[3]

A web enhancement was published on November 10, 2001. It provides a new area and a map.[4]

On January 22, 2013, Deep Horizon was given a digital re-release at DriveThruRPG, and as of November 2020 was rated an electrum best seller at the site.

Reception and influence

Influence on other works

Deep Horizon is the sixth in a series of eight adventure modules: The Sunless Citadel (2000), The Forge of Fury (2000), The Speaker in Dreams (2001), The Standing Stone (2001), Heart of Nightfang Spire (2001), Deep Horizon (2001), Lord of the Iron Fortress (2002), and Bastion of Broken Souls (2002). The concept of a series of linked adventure modules taking a character from level 1 to 20 would be come to be known as an "adventure path", a term first used by James Wyatt to describe this series in an interview in Dragon #281 (Mar 2001). Dungeon Magazine went on to publish its own adventure paths beginning in Dungeon #97 (Mar/Apr 2003). Following Dungeon's closure in 2007, adventure paths formed a core feature of Paizo Publishing's Pathfinder product line, which at one point surpassed Dungeons & Dragons in sales.

This adventure module introduced the desmodu to Dungeons & Dragons, later appearing in Monster Manual II (3e) (2002).

Critical reception

Kevin Kulp described Deep Horizon as an oldschool-style adventure module, focusing on exploration and combat. He described occasional complaints that the initial adventure hooks were lackluster, but the adventure itself was fun and offered flexibility for the DM to insert their own content.[3]



  1. Polyhedron #148 (Oct 2001), p.64.
  2. Deep Horizon. Wizards.com.
  3. 3.0 3.1 Deep Horizon (3e), Dungeon Masters Guild.
  4. Deep Horizon: The Ruined Gatehouse. Web enhancement, Wizards.com, Nov 10, 2001.
Sunless Citadel series
The Sunless CitadelThe Forge of FuryThe Speaker in DreamsThe Standing StoneHeart of Nightfang SpireDeep HorizonLord of the Iron FortressBastion of Broken Souls
Dungeons & Dragons 3.0
Core rules
Player's HandbookDungeon Master's GuideMonster ManualDungeons & Dragons Adventure Game
Arms and Equipment GuideBook of ChallengesBook of Vile DarknessDefenders of the FaithDeities and DemigodsEnemies and AlliesEpic Level HandbookFiend FolioGhostwalkHero Builder's GuidebookLiving Greyhawk Gazetteer (Dungeons & Dragons Gazetteer) • Manual of the PlanesMasters of the WildMonster Manual IIOriental AdventuresPsionics HandbookSavage SpeciesSong and SilenceStronghold Builder's GuidebookSword and FistTome and Blood
The Sunless CitadelThe Forge of FuryThe Fright at TristorThe Speaker in DreamsThe Standing StoneReturn to the Temple of Elemental EvilHeart of Nightfang SpireDeep HorizonLord of the Iron FortressBastion of Broken SoulsCity of the Spider Queen