Mystery of the Larvaenapper

From the introduction:

Ascended from the Nine Hells, a ruby eyes called Rarkaz has settled in an abandoned mine at Deadman’s Marsh and enslaved the local muscans. Now, he sets out in the midst of the night with his followers to attack the nearby insectoid settlement of Anthill, kidnapping larvae from their cradles to prepare a ritual to open a portal to the Nine Hells. Three larvae have been acquired, only two are left... Players start out arriving in the town of Anthill, and must investigate the disappearances of the larvae. Having the small town, the nearby locations and their own contacts to uncover clues leading deep into Deadman’s Marsh, past the muscan village of Buzz Town and into the mine where Rarkaz prepares.