Vulcania: The Shadow of the Squid

From publisher blurb:

"The Shadow of the Squid" is the second episode of the Xhuul saga started with "The Usual Suspects", the adventure contained in Vulcania's basic manual.

After recovering professor Kordon’s journal and risking their hides in an aerial battle, the Characters are brought to the seat of the Hornmule, faced with a key decision. Will they join the organization or return to their lives? Whatever path they take, the Characters will cross paths with the Xhuul threat again, facing a danger that could change the fate of the entire world!