 Neverwinter Nights 2 : Mask of the Betrayer is a role @-@ playing video game developed by Obsidian Entertainment and published by Atari . It is an expansion pack for Neverwinter Nights 2 . It was released in Autumn 2007 for the PC in North America , Europe , and Australia . Like the first game , Mask of the Betrayer is set in the Forgotten Realms campaign setting of the paper and pencil role @-@ playing game Dungeons & Dragons and employs the 3 @.@ 5 edition rules . 
