Eye of the Beholder

Eye of the Beholder is a grid-based, real-time first-person dungeon crawler developed by Westwood Associates and published by SSI in 1991 under the official Advanced Dungeons & Dragons licence and Forgotten Realms setting. The player leads a party of four (with up to two NPCs) into the sewers and catacombs beneath Waterdeep to confront an evil corrupting the city. Two sequels followed -- The Legend of Darkmoon (1991) and Assault on Myth Drannor (1993) -- and the trilogy remains one of the most fondly remembered Gold Box-era licensed dungeon-crawlers (Wikipedia)