An important feature of "Neverwinter Nights" is the Dungeon Master Client: a tool that allows an individual to take the role of the Dungeon Master, who guides the players through the story and has complete control of the server. Previous games such as "", based on the printed gamebooks by White Wolf Publishing, utilized this feature to a limited extent. When it was released, "Neverwinter Nights" was viewed as the first successful implementation of the feature. The DM Client allows players to participate in regular campaigns, while also allowing persistent world servers to flourish by permitting the DMs of those servers to take control of non-player characters (NPCs) in mid-game for added realism and flexibility. The Dungeon Master Client also permits the user to spawn and control masses of monsters and NPCs much in the same way as units would be controlled in a real-time strategy game.