Neverwinter Nights: Hordes of the Underdark is an expansion pack for the role-playing video game Neverwinter Nights produced by BioWare and published by Infogrames Entertainment (now Atari). The followup to the Shadows of Undrentide expansion, Hordes of the Underdark introduces a new campaign, new prestige classes, and other new features. The Windows version also includes new scripting options for the Aurora toolkit.