Darker Realms is a MUD, a multi-user text-based role-playing game, set in a medieval fantasy world. Operating since June 1990, it was one of the first LPMuds to open, and is the oldest continually running LPMud in the United States and the second oldest in the world (after Genesis LPMud). It was also the first MUD of any kind to feature a quest-based advancement system. It has been described as "one of the largest MUDs on the Internet".