Deep Ones' Doom

From publisher blurb:

Mini-Dungeon for 4–6 Character Levels 10–12

Brother Thuraz, faithful missionary of Lady Areia, has gone missing in the remote coastal village of Yarmith!

Hired to save the missionary, the player characters make their way to Yarmith, where ominous, dark clouds gather. Unbeknown to the outside world, the remote settlement has been steeped in degenerate, despicable rites for centuries.

It is one such rite that the intrepid heroes interrupt when they reach Yarmith and face an entire village and its otherworldly, inhuman benefactors:

The missionary is about to be sacrificed as a twisted wedding gift to an unholy union blessed by the Great Old Ones …unless the heroes intervene and become the Deep Ones’ Doom!