Dungeons & Dragons Online: Eberron Unlimited (commonly abbreviated DDO) is an MMORPG based on the Dungeons & Dragons 3.5 Edition roleplaying game. Developed by Turbine, DDO allows players to adventure in the Eberron Campaign Setting, a supplemental rulebook (penned by Keith Baker) to the standard Dungeons & Dragons game. Players choose from a variety of races and classes, eventually determining a selection that seems most appropriate for their play styles.
As an MMORPG, DDO actually steps outside of the box in many ways, taking some of the common mechanics of MMORPGs and supplementing them with rules taken from the D&D roleplaying game. Instead of turn-based action, DDO features real-time combat and integrated (and necessary) voice chat. Instead of being a "sit behind your computer and hit a button every now and then", Turbine wanted DDO to really stand out as a game that brings players together and emulates the true nature of D&D.
However, DDO got off to a rocky start and several server mergers have subsequently followed, albeit for the betterment of the community. DDO converted to a free-to-play model and has experienced a resurgence of interest with the gaming community. The new service offers an item shop that players can purchase items and downloadable content through as well as a premium membership, which provides the players with extra perks and a given amount of credits each month that can be used in the DDO store.