The Hidden Shrine of Tmocanotz (5E)

From publisher blurb: The Hidden Shrine of Tmocanotz is an adventure, that introduces them to an old foe making an appearance in the forsaken Izmalli Swamp on the island of Tehuatl. In a subterranean and partially submerged complex beneath the ground, the deranged worshippers of a foul deity have made a sudden and unexpected resurgence in their efforts to spread madness and wickedness beyond their isolated corner of the wetlands.