Name: Boob-Snake (Don't blame me. This is the name used by the men and it's sort of stuck)
Habitat: Underground caverns. Natural springs.
Another anatomically-perverse monstrosity. How did such horrors come to exist and why are their forms so familiar and yet horribly corrupted at the same time?
The boob-snake will usually be encountered lying in a pool of white liquid resembling milk. With the majority of their body submerged and hidden beneath the surface it's easy to mistake them for a beautiful naked woman resting in a hot spring. It's only when the boob-snake rises up out of the water that their true—inhuman—nature is revealed.
While their head, shoulders and chest are human in appearance, below there the thoracic region is repeated over and over again, so that the demon looks as though it has been extended into a snake with multiple rows of mammary glands. Mutations of this nature have been observed in annelids and arthropods, and indeed have played an important role in the evolution of some forms, but this isn't what is happening here—human anatomy simply shouldn't permit it.
Describing the 'boobs' of the boob-snake as mammary glands is technically incorrect. The 'milk' secreted by their breasts is a complex mixture of hormones and enzymes used to first render their male captives docile and then aid the boob-snake's absorption of her prey's fluids.
They lie in wait in pools of white liquid and use their alluring beauty to tempt men into approaching them. Once the man strays close enough the boob-snake will surge from the water, coil her body around them and then drag them into her pool. Boob-snake pools usually have a secret tunnel underwater leading to a more secure cave where the demon can drain her victim without being interrupted.
Once she has caught a man, the boob-snake will strip them, exude her 'milk' over their naked body and then massage them with her many breasts. These look and feel like big soft human breasts and the sensation of them rubbing all over the body is intensely arousing. Once her captive is turned on enough, the boob-snake will force them to suckle her breasts. Getting her milk inside them aids the digestion process. Enzymes within the milk painlessly break down her prey's internal organs and her intense sexual stimulation causes them to ejaculate the resultant soup onto the boob-snake's breasts in a continuous uncontrollable orgasm. The boob-snake absorbs the ejaculate through her skin. The whole process is supposedly a lot more pleasant than it sounds, but you'll forgive me if I'd rather not experience it first-hand.
Don't talk to the strange naked woman sitting in a pool of fresh milk.
Boob-snakes share similar regenerative capabilities as other demon-class HSIOs. It is relatively easy to puncture their skin with either bullets or blades, but most of these wounds will close just as rapidly as they opened. Even fire has little permanent effect.
Until we can find substances to counteract their regenerative capabilities and given their speed and strength, it is highly recommended to give boob-snakes and their pools a wide berth.
(This would be High if they ever decided to leave their pools and actively hunt us.)