The Cairngorm Peaks are a mountain range running north to south along the border of the Nentir Vale and the Stonemarch. The eastern side was inhabited by goblins and kobolds, who used it's protection to stay safe from the more savage monsters of the Stonemarch.
The Cairngorm Peaks were also the location of a rift that lead to the shadowfell. A keep was later built over this, known as the Keep on the Shadowfell.