Realm: Shadowfell
Backstory:

Nearly 200 years ago, a cult of the demon prince Orcus opened a portal to another dimention. Skeletons, zombies, and fouler creatures poured through to the realm of Shadowfell. Luckily, the Empire of Nerath dispatched legionnaires to eliminate the threat. The Empire’s soldiers destroyed the cult, closed the portal, and built a keep to watch over the location. This is known as the Keep on the Shadowfell.

Decades of peace followed, and the village of Winterhaven was built nearby. Eventually, the great fort fell into ruins. Today, it is seen as a harmless tumble of stone and wood.
If only that were true.