Found sparsely throughout the seas, these monsters have little reputation to speak of, and are often overlooked due to their rock-like appearance.
Veteran sailors, however, know what these maidens truly are, and some of the more aged sailors even know what they once were.
In truth, buried within these large stones lies the soft, inviting flesh of a mamono, their mating practice is to filter their men from the water, and then caress them within a mating chamber wherein they can nurse him with their newly acquired breasts, or something like that.
In ages past, Sailors knew to fear and treasure these massive momsters, whose flesh would rarely be harvested as a delicacy, if eaten in excess, it would poison, and so their numbers would often remain unchecked.
In the current age, it seems the amount of poison in their tissues has skyrocketed to help dissuade predation, and these lustful girls have only grown more and more abundant, spewing a cloudy discharge of eggs which their husbands have fertilized into the vast seas.
With regards to their fleshy interiors, it seems that the portion of their body which houses their husband is a repurposing of their stomach, mouth, and sex organs, and what resides within is quite similar to the interior of a sandworm, but with an increased amount of womanly bits such as breasts and hips attached to butts and vaginas replacing the plainer fleshy walls. It is said that pleasuring these leads them to reward their husbands with increased amounts of milk.
And, furthermore, from their carnivorous nature and housing decisions, one might conclude that they eat their mates, "date and dine," if you will, but much like the lovely mantis, it would seem these girls defy poor expectations.
Well, if I were truly in the business of fan made profiles, absolutely. Luckily, I don't specialise in that trade.
And referring to the girl herself, well, there's some appeal to her. The "walls covered in excess womanly bits" does rather strike me in the same manner of a mannequin in a dark room slowly pivoting it's head to face you, though.
These girls are found sparsely throughout the warmer, shallower waters of the seas, typically where many sailors are wrecked, such as near charybdis, or large coral reefs.
Because of this, they have little reputation of their own, good or bad, among humans who dwell on land, and only vague rumors at best pass the lips of human sailors.
In the ages of prior demon-lords, they were mostly harmless, even for monsters, mostly filter-feeding and occasionally consuming sunken sailors, their largest source of food was fools who hunted them for their delicious, succulent, nutritious flesh; likely made so intentionally to lure in humans for culling.
In the present age, where monsters eat up humans in other ways, their flesh has become highly poisonous, and the smallest bite spells death for any who consume it.
Because of this, the entire industry of harvesting them has rapidly vanished, and the fishing industry has begun to leave reefs bare.
These Mamono, now thoroughly infused with a new kind of hunger, aggressively swallow humans in search of spirit energy.
In ages past, it was not understood how they reproduced, but it is believed that they are much like slugs and snails, as evidenced by their skillful ravishing of men, for their ability to produce spirit energy, and their pleasuring of women to extract it from the air.
Using captured women as surface lures, these mamono incite their orgasmic cries to lure sailors towards them, because of this, charybdis are more content to have *them* near than to have other mamono nearby.
The few men who return from partnerships with these lustful stones spin yarns reminiscent of Sandworm marriages, speaking of soft, crowding, dripping women who hold them close and move about, enticing them.
No light shines within their body cavities when they are unharmed, and no dissections have been undertaken, but it is believed that the cavities in which men are stored are a fusion and repurposing of digestive and reproductive organs.