From the introduction:
Two generations past a Paladin order of the God Tyr used the Twilight Citadel as a stronghold, which dominated the local trade route between the nations of Highwood and Stonewater. The two nations had always been rivals but were on relatively friendly terms joined in their common belief of Tyr. This was rent asunder when a new Lawful Good holy order, that of Athena came to the area and swiftly begun to convert the local population of Highwood to its side. This eventually led to a religious civil war in the region and the eventual separation of the lands into two camps of belief.
Geographically the two nations have been set apart by the Needle mountains an offshoot of the greater Spiral Peaks mountain chain. With only a few sparse trade routes thru them and no discernible passage otherwise, the few trade routes that did exist were important to both nations. Thus the Twilight citadel that sat upon a lone hill within a valley acted not only as a trade route monitor but also as the faiths headquarters in the region.
The civil war that swept the land some fifty years ago lead to the Citadel of the Tyrians being eventually besieged, breached and all therein slain. Once conquered the citadel quickly fell into disuse as the Athenians moved on in their solidification of their dominance of the faith of Highwood. Unfortunately one of the slain men of Tyr refused to take his journey to the afterlife and becoming consumed by the desire for revenge began to bring his hatred to bear on all those he considered as his enemy.