From publisher blurb:
The region of Kael'Myn was once home to a terrestrial enclave of celestials, barred from the heavens. Since that ancient realm's demise the region has become home to a plethora of peoples, monsters, and power hungry organizations. Powerful relics wait to be discovered by adventurers daring enough to brave the dangers of Kael'Myn's shadowy underworld, and a new war is brewing that threatens to sweep every last individual in Kael'Myn into a catastrophe the likes of which hasn't been seen in centuries.
All this is included in Regional Settings: Kael'Myn plus:
A new race and new exotic weapon
2 new spells
3 new monsters
9 new feats
4 detailed organizations
A detailed history and description of the region, its history and people, complete with full color maps and a timeline for easy reference