Inquisitor is a tabletop miniatures game based in Games Workshop's Warhammer 40,000 Universe, developed by Gav Thorpe and released in 2001. Whereas Warhammer 40,000 focuses on squad-based tactical warfare, Inquisitor focuses on a small group of adventurers. It is like a Role-playing game, requiring a gamesmaster and featuring complex D100 mechanics and suggesting campaign narratives between games. Inquisitor had its own website and 54 mm scale models were available as "Specialist Games" from the Games Workshop catalogue. Since being discontinued by Games Workshop, Inquisitor lives on as Inq28, to which John Blanche contributes, and Inquisimunda, both adopting the Inquisitor ruleset to 28mm models.  
Players choose a warband, usually made up of an Inquisitor and his/her henchmen, but also potentially led by any of a huge variety of rogues and heroes from throughout the Imperium such as Rogue Traders, Space Marines or Tech-priests. It even offers the chance to take on the guise of some of the Imperium's greatest enemies, such as Chaos Sorcerers, Genestealer Cult Leaders or twisted Mutants.
The game is supported by Games Workshop's Specialist Games division, which periodically releases new rules for the game through the Specialist Games website. The game is intended for older wargamers, aged 16 and up.
The Inquisitor rulebook is available as a hard copy from Games Workshop, or as a PDF from the Specialist Games website. It gives very rich and detailed information about the Inquisition and the WH40K universe in general. The name, when written, is sometimes shortened to =I= by fans, or =][=, or -][- in homage to the symbol of the Inquisition as depicted on the cover of the rulebook.
Inquisitor uses a rules system based around the throwing of two 10-sided dice (known together as a d100 or d%), generating a percentile value, with one die representing the "tens" and the other representing "units". Standard six-sided dice are used for several of the game's mechanics also.
There are, technically, no limitations on the effective power and equipment of a player character - there are no hard and fast rules that prevent a player from creating a character armed with terrifyingly potent combinations of equipment and skills, although the game rulebook includes an optional "points" system that the organisers of a campaign might use to limit or guide their players. The expectation is that players exercise common sense when creating their characters. Unlike a tactical wargame or Role-playing Game, Inquisitor describes itself as a "narrative" skirmish game, and the emphasis is on spinning a good story along the lines of a great action movie or adventure novel, rather than focusing on winning at all costs.
There are a few additional companion rulebooks for the Inquisitor game:
- Thorian Faction Sourcebook:
- This book details the background and history of the Thorian philosophy and those who follow it. Amongst other topics, the book focuses on the efforts of Promeus, a semi-legendary figure from the earliest days of the Imperium, and his desire to revive the Emperor of Mankind from his half-life existence on the Golden Throne. It traces his, and his followers the Promeans', attempts to achieve their end and conflict with their allies and later rivals led by Moriana. After thousands of years, the two factions slowly disappear, but their history and achievements have paved the way for two new factions, the Thorians and the Horusians, to rise and seek out a new way to approach the divine nature of the Emperor.
- The book details additional characters and how the followers of the Thorian philosophy interact with other Ordos of the Inquisition. It also provides additional weapons and powers to be used by the newly introduced Thorians.
- The Cirian Legacy: details the planet of Cirian V that is controlled by Tech-Priests of the Adeptus Mechanicus. Inside are 3 individual campaigns, lists and details on important characters, groups that deal with Cirian V, and background on the Scarla sector surrounding Cirian V. The campaign begins as a simple mission for the players to discover why the Adepts of the Conclave have ceased paying their Imperial tithes. But as things get nasty - in a mess of rioting miners, psychotic tech-priests and hallucinogenic smoke - will the players notice that something even more sinister is afoot?
- Death of an Angel: contains three different campaigns. Set on Karis Cephalon, the campaign guides the players both as allies and opponents in a storyline that begins with a simple mutant uprising, but swiftly turns sinister. Who is trying to release the daemon Phraa'gueotla and why? And can there really be any substance to rumours of a pre-Imperial superweapon - the Angel - hidden somewhere beneath the planet's surface?
- Heavenfall: contains two campaigns with details on important characters and background. The machinations of Inquisitors Scarn and Lichtenstein have collided on the once-beautiful Equinox. But with a rogue assassin on the loose and the enigmatic Eldar taking an interest in a world that was once theirs, the players will have to keep their wits about them to get away from this one...
Player characters are usually represented in-game by 54 mm miniatures purchased from Games Workshop, roughly twice as large as the standard 28 mm Heroic scale of WH40K miniatures. The models available represent existing characters (such as Witch-hunter Tyrus, or Inquisitor Eisenhorn) presented in the rulebook. Players wishing to depict their own unique characters are generally required to extensively convert their models, or give them unique paint schemes. However, the distances given in the rulebook are written as yards, so that players can use any scale of miniature they wish, including the same models with which they play standard Warhammer 40,000.
There are many different groups that players can play. Presented here are the archetypes represented in the Rulebook:
- The Inquisition: An order that defends the worship of the Emperor of Mankind and defends the Imperium from its alien and heretical enemies.
- The Adeptus Astartes: They are the "Space Marines," a legion of warriors that serves the Emperor of Mankind and operate as a powerful army of genetically altered super humans.
- The Adeptus Mechanicus: They are the engineers of the Imperium and are focused primarily on technology and research.
- The Rogue Traders: They are bands of merchants adventurers, or similar people, whose allegiance may vary.
- The Cultists and Fanatics: Street preachers and zealots who mostly serve the Ecclesiarchy and worship the Emperor of Mankind.
- The Imperial Guard: Represent the average soldiers of the Imperium, and unlike the Adeptus Astartes, they are most often normal human beings.
- Desperados: Gunslinging rogues, kin to Rogue Traders, their allegiance may vary.
- The Enforcers: They serve the Imperium but may also operate as independent/rogue groups under the command of a disloyal commander of an individual ruler of a world.
- The Mutants: Mutants are humans either warped by the power of Chaos or mutated due to genetic deviancy. They are hunted down by Inquisitors who deem any mutation as a threat against humanity and the Imperium.
- The Ecclesiarchy: The priest/religious organization of the Imperium and worship the Emperor of Mankind.
- The Arco-Flagellant: Heretics deemed by the Ecclesiarchy to gain redemption through using themselves as mindless living weapons against the enemies of the Imperium.
- The Assassins: Trained warriors who specialize in assassinations in the name of the Emperor of Mankind.
- The Daemonhosts. Daemonhosts are Daemons which are imprisoned within a human body. Mostly these will be used by the inquisition or chaos cults.
With the release of Inquisitor came two reviews by RPGnet.
The first, in July of 2001, was written by Charlie Engasser on the product. In his review, he states that the good aspects of the game are that "the production values as far as the printed material are excellent" and "Anyone familiar with the Warhammer universe will be pretty much at ease here." On the other hand, he describes the bad aspects such as the cost of the game and stated that "Completely ignoring races like the Space Orks, Eldar and most importantly, the Tyranids is a pretty glaring omission."  The later release of random character generators (such as in White Dwarf Magazine, issue 258 and the second issue of the Inquisitor supplement Exterminatus) has partially rectified this problem, as well as the release of a supplement specifically describing a campaign against the Eldar.
The second, in August 2001, was written by Sean Broughton-Wright on the game mechanics and playing. After noting problems with the variability of product quality ("the usual excellence displayed in such figures as Artemis to the rushed look of some others like Slick Devlan") and complimenting the quality of artwork ("all the good stuff that you'd expect of a Games Workshop product set in the 40K Universe"), he discusses the mechanics; he states, "The great strength of the GW game in its gearing towards competitive play is understandably missing here. As a war game it isn't very successful either." Among other issues, he was "bogged down in rules" and that he "Can't help but feel this would have been better as a first person shooter." This revolves around the issue that he points out, that "There seems to be very little support, even when compared to other sideline games like Mordheim."
- ↑ 1.0 1.1 Specialist Games. Games Workshop. Retrieved on 2007-05-29.
- ↑ 2.0 2.1 Games-Workshop Online Store. Games Workshop. Retrieved on 2007-05-29.
- ↑ The Conclave. Retrieved on 2016-05-13.
- ↑ 'Inquisimunda Resources', Empire of Ghosts. Retrieved on 2016-05-13.
- ↑ 5.0 5.1 5.2 Thorpe, Gav (2001). Inquisitor, 1st Edition, Nottingham: Games Workshop. ISBN 1-84154-077-3.
- ↑ 6.0 6.1 Thorpe, Gav. The Thorians: Faction Sourcebook (PDF). Inquistor Rulebook. Games Workshop. Retrieved on 2006-03-28.
- ↑ RPGnet: The Inside Scope Capsule. RPGnet. Retrieved on 2007-05-26.
- ↑ RPGnet: The Inside Scope Mechanics. RPGnet. Retrieved on 2007-05-26.