Ubisoft's official Shadowbane website has been updated with a detailed overview of the upcoming Throne of Oblivion expansion. Check it out:
...all of the new faces appearing in Throne of Oblivion aren't villains. To counter the new undead threat, the Nightstalkers have come to take up arms against the dead. The Nightstalkers were an ancient order, trained by the Titans of Ardan to serve them as scouts and spies. When the hordes of angry dead arose during the War of Shadows, the Nightstalkers devised a new style of fighting, and armed themselves with new spells and techniques to fight the darkness. When the War ended, the Nightstalkers knew that someday Oblivion might ravage Aerynth again. No vault, no book could be entrusted to last forever, and so the thirteenth Titan wove a mighty spell, placing twelve of the mightiest Nightstalkers into a magical slumber and removing them from the world, to some hidden realm born of magic. When the Isle of Oblivion appeared, the Nightstalkers awoke. Daunted by the scope of the undead invasion, the Nightstalkers have decided that their greatest weapon is not their blessed stakes, but their knowledge. The original Nightstalkers scattered, journeying to every land to serve as teachers and trainers, in the hope that every realm can raise armies of new Nightstalkers and drive the unholy shadow from Aerynth once and for all. Armed with their special fighting style and various holy powers designed to break the powers of Vampires and hold the unholy at bay, Nightstalkers offer the brightest hope in the face of the Lich-Queen's onslaught.