Realms, both wondrous and dire, border the world. One such realm is the Shadowfell. Although not inherently evil, the Shadowfell is fraught with dangers and the barrier between worlds is thin. Sometimes the darkness breaks into the light.
Nearly two hundred years ago, a cult of the demon prince Orcus purposely created such a gap, connecting one of Orcus' unholy shadowfell sites to the world. Skeletons, zombies and fouler creatures flooded through the rift into the light of day. The empire of Nerath dispatched legionnaires to eliminate the threat. The empire's soldiers destroyed the undead, sealed the opening and built a keep to watch over the location and contain the threat. This is the site known as the Keep on the Shadowfell.
Decades of peace followed, and the village of Winterhaven arose within sight of the keep. Eventually the great fort fell into ruin and its' grand purpose was forgotten. Today, it is seen as a harmless tumble of stone and wood.
If only that were true.