Dungeons & Dragons Online (DDO) is a massively multiplayer online role-playing game (MMORPG) developed by Turbine, Inc. for Microsoft Windows, and originally marketed as Dungeons & Dragons Online: Stormreach, then Dungeons & Dragons Online: Eberron Unlimited with the start of Free to Play, changing to Dungeons & Dragons Online with the introduction of Forgotten Realms related content. Turbine developed DDO as an online adaptation of Dungeons & Dragons (D&D) based loosely on the D&D 3.5 rule set. The game is set in the unexplored continent of Xen'drik within the Eberron campaign setting.
Centered in the city of Stormreach, DDO is set on the fictional continent of Xen'drik, in the world of Eberron, a Dungeons and Dragons campaign setting. Xen'drik is a vastly unexplored and wild locale, once the center of the Advanced Giant Civilization, which was destroyed thousands of years before. Players can create their characters following the revised edition of D&D 3.5 rule-set fashion, and play them in both indoor and outdoor environments, including dungeons.
Although the game is based in large part on the tabletop D&D 3.5 rule set, it contains changes, some which were introduced due to differences in the dynamics of video game combat and tabletop gaming. For example, Turbine wanted DDO to use a real-time combat engine, whereas tabletop D&D uses a turn-based system. This meant considerable changes in the handling of combat, character skills, and feats—areas where Turbine felt the turn-based combat system and real-time combat did not mesh. Differences include increased hit possibilities in a round (as much as twelve times more), increased spell casting resources over rest periods, and the use of a spell point system instead of spell slots. Magical items are low cost (they average 1/8 of the tabletop D&D prices), characters have higher stats, and offensive effects created by characters do not harm their allies.
The game is set in the city of Stormreach, a giant-scaled city built ages ago, and recently settled by humans. Areas in Stormreach are the Harbor, the Marketplace, and five Dragonmarked Houses (House Cannith, Deneith, Jorasco, Kundarak and Phiarlan). Adventures and quests are available beyond the city walls into other areas across the continent.