The game is set in the pseudo-medieval kingdom of Ehb, 150 years after the events of Dungeon Siege and follows descendants of survivors of the 10th Legion in their quest to reestablish their military force.

The game was instead developed by Obsidian Entertainment with Chris Taylor, the inventor of the Dungeon Siege franchise, serving as an adviser.

As such, unlike previous games in the series, Dungeon Siege III no longer features an automatic targeting system and point-and-click mechanics.

In addition, there are three different special abilities for each stance[4] that require "focus", the game's equivalent to magic points, to use.

Additionally, players collect experience points for defeating enemies and completing quests which in turn increase the character's level.

[7] Items can be obtained as a reward for winning fights, looted from fallen enemies and bought with gold, the game's currency, from vendors, special non-player characters that can be found in various locations.

[4] The game takes place in the fictional Kingdom of Ehb in a high fantasy world, roughly 150 years after the events of Dungeon Siege.

A small group of legionnaires remained, led by a man calling himself the Venerable Odo, a former Legion spy.

After fighting more of Kassynder's forces, the player travels to Stonebridge City to reopen the Legion's Grand Chapter-house there as a sign of their resurgence.

After prevailing against Kassynder in battle, she is revealed to be an archon who was seeking to reawaken her long lost masters in the Rukkenvahl Forest, but only managed to create a mutant god.

[14] Square Enix announced in June 2010 that they commissioned Obsidian Entertainment, which had previous experience creating role-playing games such as Neverwinter Nights 2 and Fallout: New Vegas, with developing Dungeon Siege III.

[16] For Dungeon Siege III, Obsidian used its own proprietary Onyx Engine, allowing the developers to create graphically appealing settings.

[24][25] A three-issue mini-series also titled Dungeon Siege III was released digitally by Dark Horse Comics.

[26] After the release, a number of players complained about the controls on the PC version of the game,[27] prompting the developer Obsidian Entertainment to address those concerns.

The story follows the protagonist(s) on a journey to Aranoi desert, where an undead outbreak is taking place, in search of a long lost Legion spy and the mysterious "greatest treasure of the Azunite church".

[5] The voice acting received mixed responses, with Memeburn remarking that it helps the characters more than the story does[13] while Joystiq called it "horrible".

[6] Reviewers also lauded the game's AI controlling the player's companion for acting both autonomously and effective and how the various characters complement each other.

[2] Reviewers also liked the multiplayer system, explicitly noting how easy it is for others to join, while also bemoaning that progress is not saved for other players.

[7][2] Memeburn on the other hand considered multiplayer a "waste of time" and criticized Obsidian for forgetting to implement obvious safeguards, mentioning that anyone can join a game and sell off all the player's items before exiting again.

[13] The restricted camera in co-op mode, forcing all characters to be on the same screen, was criticized by many reviewers as unnecessarily limiting and potentially confusing.

"[49] Edge gave the PlayStation 3 version a score of seven out of ten, saying, "It's a game built from pluck and resourcefulness, in other words: thoughtful when it can afford to be and stoically reliable – for the most part – when it can't.

Club gave the Xbox 360 version a B+, saying, "Dungeon Siege III isn't extraordinary, but is it a highly satisfying way to spend time gaming with a friend or three.

"[53] Susan Arendt of The Escapist gave it three-and-a-half stars out of five, saying, "I love playing Dungeon Siege III despite its many flaws, and if you don't mind that the overall experience is pretty shallow and meant for single player, you probably will, too.

"[45] Marc Saltzman of Common Sense Media gave the PlayStation 3 version a score of four stars out of five, calling it "a fun and frantic 'RPG lite' with great co-op play.

"[54] David Jenkins of Metro gave the same console version a score of seven out of ten, saying, "The best Dungeon Siege ever is a more of a compliment than you might think in this accessible and fun action role-player.

"[55] However, Mark Langshaw of Digital Spy gave it three stars out of five, saying, "One of the most disappointing aspects of Dungeon Siege III is the seemingly pointless restrictions imposed on co-op play.