A monster with a lower body like that of a slug, which prefers dark and damp places. Originally they were shelled monsters, but the shell was getting in the way, so they discarded it through the process of evolution in order to obtain even more pleasure.
When they spot a man that strikes their fancy, their mating instinct takes over and they slimily crawl across the ground, heading in a straight line for the man. However, they have extremely leisurely personalities and their movement is slow as well, so if one runs right away, there probably won't be any danger. But no matter how docile they may be, one must never approach them. Their body is always covered in slimy, sticky mucus. If a man approaches, he'll get caught in the slimy mucus and then, with his movement snared, they'll climb over him with their mucus covered lower body and have sticky sex.
When having sex, they caress the man's body while smearing the sticky mucus all over every inch of it. If they paint him with the mucus, then their slimy body will become able to stick to his more persistently and they'll be able to give him a taste of pleasure that will leave him wanting more. This mucus overflows from their vagina as well, and during coitus it covers the penis and is drawn out into strings while they continually provide sticky pleasure while making lots of obscene noise. Additionally, they prefer to have sticky sex over a long period of time. Once they start having sex, it may take several hours, or even an entire day before the dull wet noises stop.
Since the rise of the current Demon Lord, only females have been confirmed, but it seems they were hermaphrodites in the past. Perhaps as a vestige, it seems that rarely, when they spot a human woman, they'll shower her in mucus without much thought and make her all sticky.
Their sticky body is vulnerable to salt and if their body is covered in it, their moisture will be absorbed and their body will shrink into a child-like form. It doesn't kill them and it doesn't cause pain or anything similar, but since they'll try to reclaim the moisture they lost by being showered in a man's semen, in contrast with their child-like appearance, they become even more aggressive about attacking men.