The Last Defender

From the introduction:

The Last Defender of Genmarr Pass is an adventure designed for a group of four to six characters of fifth to seventh level. After reading the Player Background (found on the back of the outside cover), read the module at least once to familiarize yourself with the various encounters before proceeding to play. The player characters can be of nearly any race or class.

The PCs are not initially privy to the background information, but may learn it during the course of the adventure.

The adventure begins as the party is making its way through a recently reopened pass in an ancient mountain range.