The Lost Temple of Forgotten Evil from Dark Naga Adventures might have a rather generic name, but it actually deals with the PCs coming across of a cult of Hastur (the Cthulhu Mythos deity) and presumably foiling its plans. I a big fan of the Cthulhu Mythos (my 2nd favorite RPG is Call of Cthulhu) and incorporate Mythos themes into my own game.
Hastur is perhaps the trickiest deity of them all, because it's not entirely clear that Hastur is even a deity in HP Lovecraft's own works. Though he made mention of the name, clearly referencing Robert W. Chambers work, most notable many of the stories mentioned in the King in Yellow. But Chambers work is eerie, surreal, even sensual, perhaps best captured in Karl Wagner's The River of Nights Dreaming. But ignoring all that, August Dereth made Hastur just another squid god, like Cthulhu.
