Beyond the Rune Gate (2005)

`From the introduction:

At the end of the Age of Demons, just as the Giants began their rise to power, one fire giant struck a bargain with a powerful fiend, before the couatls could manage to bind him to the depths. This giant prince offered to hide the demon until after the scourging was complete. Seeing his imminent captivity, the fiend readily agreed. Little did he know that he was trading one form of captivity for another, as the hiding space was within the giant princes crown. Once the fiend was bound into the crown, the giant prince reneged on his bargain and used the knowledge of the demon to amass terrific power and attain everlasting life. Hidden away in a secret fortress deep in a jungle valley, the giant prince dreamt far greater dreams of conquest and total dominance.
...
"Having left Stormreach four days ago, the object of your exploration stands before you. Durvan learned of this place from another explorer, and hoping to lead in its discovery, brought your group to Xen’drik to explore the mysterious Ice Valley. In this valley you found a great fortress adorned with strange runes—or rather glyphs—after defeating the undead dragon guardian your now ready to study these strange symbols and try and eke out their meaning."