The Eye of Chentoufi (OSR)

From publisher blurb:

The Oculus of Senrahba is one of ancient and powerful relics used centuries ago by the Ydrissid Empire to grant them mastery over the elements. As the empire of Ydrissid crumbled, the artifacts were eventually lost and spread to the wilds across Okkorim.

In part one of this three-part series, involving the Occulus of Senrahba, the first part of the larger Lamentation of the Ydrissid campaign, the adventurers find themselves in a race against competing groups. One who wishes the power of the Ydrissid to remain lost and forgotten, and another who seeks the potent artifact for themselves.