Smuggler's Bane (Arrowflight) (2003)

From the introduction:

In Smuggler’s Bane, the heroes are hired by the local authorities to root out a band of smugglers operating out of a nearby cave complex and circumventing the King’s import and export taxes. The smugglers have successfully eluded all attempts by the authorities to bring them to justice, until now. Acting on information gleaned from an insider, the heroes journey to the gang’s hideout in a cave complex where they are to bring them to justice. The adventure is not quite that simple, however, for on the night before the heroes attack the complex, another foe beats them to it. Unbeknownst to the heroes or the smugglers, a group of renegade coriphae, called phaciore, have a secret temple deep in the caves. The phaciore attack the smugglers in the dead of night, dragging them off to be sacrificed to their primeval god—a giant crab. The heroes arrive to find the caves deserted, with signs of a struggle and a trail leading them to the phaciore secret temple just in time for a smuggler sacrifice.