Source: Wikipedia, "Dungeon_Master_(video_game)," available under the CC-BY-SA License.
"Dungeon Master is considered to be the first 3D realtime action computer role-playing game, published in 1987 for the Atari ST by FTL Games. It reportedly sold 40,000 copies in its year of release alone, and went on to become the ST's best selling product of all time, reaching an astounding market penetration of more than 50% of the Atari STs ever sold.
An almost identical Amiga version was released the following year that was the first computer game to use 3D sound effects. The game was also ported to PC, Apple IIGS, TurboGrafx-CD, SNES, Sharp X68000, PC-9801 and FM Towns and translated from English into German, French, Japanese, Chinese and Korean.
While previous games such as Alternate Reality: The Dungeon, The Bard's Tale, Ultima and Wizardry offered Dungeons & Dragons-style role playing, Dungeon Master established several new standards for role playing and computer games in general. Dungeon Master was a realtime game instead of the traditional turn-based approach that was prevalent until then. Instead of using text-based commands to interact with the environment, players directly manipulated objects and the environment by clicking the mouse in the enlarged first-person view. Abstract Dungeons and Dragons style experience points and levels were eschewed in favor of a system where the characters' skills were improved directly via using them. It also introduced some novel control methods including the spell casting system, which involved learning sequences of runes which represented the form and function of a spell's effect. For example, a fireball spell was created by mixing the fire symbol with the wing symbol. This kind of attention to detail and focus on the user interface was typical of the game and helped create an often captivating sense of craft and ingenuity. Other factors in immersiveness were the then-revolutionary use of sound effects to indicate when a creature was nearby, and (primitive) dynamic lighting."