The Bloodstone Wars (1987)

For Character Levels 17-20

From the back of the module:

What strange role does Orcus, Prince of the Undead, play in the invasion of peace-loving Damara? And what interest does the Grandfather of Assassins have in the tiny Barony of Bloodstone Pass?
With this adventure your player characters inherit an entire Barony - with a recently-reopened mine that produces immense wealth. Wealth enough to attract the dangerous attention of their neighbors...wealth enough to attract the attention of the Witch-King of Vaassa...and Orcus himself!
Now, your tiny barony is the pivotal point in a war that threatens to engulf the entire Forgotten Realms. Take Command, and defend yourself against the encroachment of the evil, demonic forces of the nightmare realm of Vaasa.
A large, four-color map of the region makes your new realm come alive. Wild and wooly BATTLESYSTEM scenarios (with options if you're not into miniatures) give you the full range of battlefield excitement!
Come learn why high-level AD&D game play can be much more than just monster bashing. The Army of Bloodstone Pass wants you!