Neverwinter Nights 2: Mask of the Betrayer is a 2007 role-playing game exclusively for the PC and is the expansion to 2006's Neverwinter Nights 2. Unlike the first entry in the series, Neverwinter Nights (2002), the game was developed by Obsidian Entertainment and not series creator BioWare.

Mask of the Betrayer takes place immediately after the events of its predecessor, 2006's Neverwinter Nights 2. With the King of Shadows defeated, the player awakens in a mysterious holding cell in a cave. A red wizard named Safiya approaches you and takes you to her mother Lienna, located in the town of Mulsantir. During the journey to Mulsantir, a powerful and unknown spirit awakens in you, and consumes a bear spirit god named Okku. Upon reaching the city, the player discovers that Red Wizards are attacking Safiya's theater company, called The Veil. In the backroom of The Veil theater house the two go through a portal leading to the Shadow Plane, where the Red Wizards have killed Safiya's mother. With the help of Safiya, the player eliminates the Red Wizard threat, but discovers a startling reality: you are turning into a Spirit Eater, a powerful spiritual force that will ultimately consume you unless you learn to harness its power.