Ancient Domains of Mystery is a roguelike video game designed and developed by Thomas Biskup and released in 1994. The player's goal is to stop the forces of Chaos that invade the world of Ancardia. The game has been identified as one of the "major roguelikes" by John Harris.^[1]

Like the original roguelike games, Ancient Domains of Mystery uses ASCII graphics to represent the game world. A later version added the option to play with sound, tile-based graphics, and an overworld map.^[2] Most dungeons are procedurally generated, but once the game generates a dungeon, it does not change even if the player exits and re-enters it.

Biskup ceased development of the game for nine years and revisited it in 2012. He then resumed work on a sequel, Ultimate ADOM, an engine for future roguelike games. Biskup first made an updated version of Ancient Domains of Mystery available to sponsors of his crowdfunding campaign. Later versions, beginning with v1.15.2.r60, were released on the internet and through digital distribution services.

Ancient Domains of Mystery takes place in the fictional world of Ancardia, in the mountainous Drakalor Chain. For 6,000 years, the world has known relative peace, but recently reports have spread of the appearance of dangerous dungeons and frightening monsters. Khelavaster, a wise sage, discovers an ancient prophecy regarding the Coming of Chaos and propagates it to the peoples of the world. It speaks of a champion who will defend the world from the forces of Chaos in the Drakalor Chain.

Hearing of this prophecy, many would-be heroes set out. The player assumes control of one such adventurer. Ancient Domains of Mystery has multiple endings which consist of closing the Chaos gate, becoming a demigod, or committing a heroic sacrifice to stop the Chaos invasion.^[3]

Ancient Domains of Mystery presents an initial choice of one (male or female) player character from twelve races and twenty-two character classes, the combination of which strongly affects gameplay, in both subtle and obvious ways. Among other traits, character development includes experience levels, statistics, and skills. Version 1.1.0 introduced a talent system,^[4] allowing further customization of characters, based on a hierarchical system of prerequisites.

During adventures, a player is likely to explore many areas and complete multiple quests. Which quests are available may depend on character experience level or alignment (lawful, neutral, or chaotic). Alignment also affects NPC and deity interaction with the character. How one solves a quest can also affect one's alignment, such that a chaotic character seeking redemption can eventually become lawful through his or her actions (or vice versa).

Ancient Domains of Mystery offers multiple ways of winning, which vary in difficulty. The regular ending that appeared first during development consists of locating and closing the gate through which the forces of Chaos infiltrate Ancardia. The player also has the option to enter the gate, providing access to special endings, which are generally considered more difficult to accomplish. Ancient Domains of Mystery's quest-centric, plot-driven structure owes as much to adventure games like Zork as to the hack-and-slash of sibling games like Angband.

Development of Ancient Domains of Mystery started on 12 July 1994 and continued steadily until 20 November 2002.^[4] Core development on the game stopped with the release of version 1.1.1. Beta-quality ports to Mac OS X of this version appeared in 2006.^[5] Plans for future versions had not at that time been announced, but a next-generation successor to Ancient Domains of Mystery, called JADE,^[6] started development and betas have since been released. The developer later renamed Jade to Ancient Domains of Mystery II, leaving Jade as a game engine name.

In July 2012 a crowdfunding campaign was initiated by Thomas Biskup to resurrect Ancient Domains of Mystery development. The campaign reached its initial goal of $48,000 on 22 August, 51 days after starting, and finished at $90,169.^[7] Ancient Domains of Mystery entered the Steam Greenlight in May 2014.

As of April 2017, a classic version is available at the main site free of charge, with two variants: the text-only version with wide platform support, and the graphical version (which also includes text-only mode) for Windows, MacOSX and Linux. A paid version is available on Steam as Ancient Domains of Mystery Deluxe with enhanced gameplay features and gameplay customization.

Although Ancient Domains of Mystery classic version is available free of charge, in difference to most roguelikes its source code is unavailable. Despite earlier announcing that the source code would be published after the release of version 1.0,^[8] Biskup later chose to reserve it for himself in order to retain some mystery about game operation and to curtail the spread of unsanctioned variants.^[9] Despite this stance, he is open to licensing the source to capable developers to form a commercial venture.^[9] Players meanwhile have deduced underlying mechanisms through careful experimentation and reverse-engineering by inspecting the execution flow, memory and binaries of the game.

Biskup credits his game's community following as the main reason for both of his games existence.^[10] He emphasized the importance of listening to their ideas and said he received great feedback from them through the years of development.^[10] Though most of his fan encounters are positive, he stated that he received death threats when he declined to release the game's source code and on one occasion, keen fans stalked his house.^[11]

Ancient Domains of Mystery has established a strong fan base that started gathering since 1997 at Usenet group rec.games.roguelike.adom, sporting 2,000-3,000 messages monthly in years of active development, although lately the activity has been ceasing.^[14]

Given that Ancient Domains of Mystery was a long-lasting development effort and new versions of the game were regularly released over the years,^[15] Ancient Domains of Mystery has received many critical reviews over many varied versions. The overall critical reception is good.

Reviewers usually compare Ancient Domains of Mystery to other roguelike games (like Rogue, Angband or Moria) and find that Ancient Domains of Mystery offers a much deeper storyline, more manifold environment,^[16] and is generally more complex.^[12] Most note that Ancient Domains of Mystery offers very high replay value^[17] and general randomness of events that happen in the game.^[2][13] Overall game system design (and especially the character development system) is usually praised for its flexibility.^[12][13] Some reviews note low hardware requirements and freeware distribution as essential advantages.^[17]

The user interface is cited to have high learning curve by some critics,^[12] while others note that it is "brilliant in its simplicity", "very practical" and "easy to navigate".^[13] Keyboard controls imply usage of the numeric keypad which makes Ancient Domains of Mystery relatively hard to play on keyboards without keypads (i.e. some laptop keyboards).^[12] Discussing gameplay, the same complexity and randomness that were cited as positive features are sometimes said to make Ancient Domains of Mystery very difficult for beginning players.^[2][17] Most reviewers agree that Ancient Domains of Mystery may be very hard to play for beginners due to the deletion of savefiles, which is uncommon for games outside the roguelike genre.^{[2][12][13][17]}