From the publisher's Web site
Are you looking for adventure? Do you have a friend who has always wanted to join you on an epic quest? Neverwinter Nights Diamond Edition is the perfect way for new heroes to begin their journey!
For one low price, enjoy everything the original game has to offer, as well as all of the added features in the Shadows of Undrentide and Hordes of the Underdark expansion packs, plus the Neverwinter Nights Kingmaker expansion, which includes three complete BioWare designed adventures!