In deep, undisturbed forests around the world, there is a species that has spread on the periphery of human society. It has many names across the cultures that have grown alongside it , though the few scientists that study it have dubbed it Particiventer gremii. It is nigh impossible to find if one isn't looking for it, but if one asks the right question, a local guide will point them in the right direction. In many places it is recommended to take a few days worth of good food with you, and almost always advised to bring a hairbrush.
This species is long lived, estimated to reach 200 years in age. They are tall, typically a foot or two above the average person, with thick brindled fur covering its body and a mane running down its sloped back. It lopes on all fours with long forelimbs, though it can manage a slower biped gait on its digitigrade hind legs. At the end of those forelimbs, its four fingers terminate with long, spade-like nails. Its snout is long, sloping gently down from its forehead, good for scenting out a meal or a curious human. It has teeth not unlike a badger's, though its canines are long enough to nearly resemble a pair of tusks. Its ears are small disks to the side of its head, and it has golden-brown eyes that reflect even the smallest amount of light. At last, its tail is long and shaggy.
When located, if the human is found suitable and offers a meal, the creature will bring them back to its nest. They build semi-permanent woven structures of branches, often filled with moss or some other soft bedding. Mutual grooming is highly important; it is speculated that P. gremii coevolved with humans with this as a primary social bonding method.
The biology of this animal is the most important reason why it is sought out. P. gremii are exclusively female, and only reproduce with humans. The method used to bear their young is beneficial to both parties, though poorly understood. These creatures cause a mutual pregnancy with a human that forms a temporary social bond with them. P. gremii will become pregnant with the human's offspring, while the human's womb will grow with 1-2 of the creature's cubs.
Reproductive events occur after grooming, it is important that one to two hours is spent cleaning and combing the tail, mane, and fur. Once satisfied, the P. gremii will make contented, deep rumbling noises akin to a cat's purring. A structure akin to a cloaca will be pressed against the human's opening and two hemipenal structures will be everted into them. The creature will cause sexual fertilization over the course of 30-50 minutes. A night will then be spent with the creature, typically with tail or body wrapped around the human to provide warmth.
Pregnancies last 10 months. The human will experience symptoms typical of a normal pregnancy, with the addition of a sharply heightened sense of smell, increased body hair, and increased muscular tone. The cubs within the parent's womb grow fairly large, with a singleton pregnancy appearing as human twins by the eight month, and a twin pregnancy appearing as triplets or quadruplets by the same time. Offspring are far more active that human fetuses, moving as early as the second month and by month five cause significant warping to the belly at most hours of the day. It is recommended a diet high in tubers, mushrooms, and red meat to curtail some movement. The cubs will also produce deep vibrations while inside the womb, which, while not audible to outside observers, can be felt resonating through the parent's womb.
P. gremii develops its human baby for 10 months. Its lower abdomen swelling greatly and fur thinning slightly. Its baby similarly shows higher amounts of movement, and remote observation research shows that it spends a good portion of its time grooming and humming deeply to the baby within its womb. One pairs of teats will develop on its lower chest, and analysis shows its milk is 94% similar to that of humans.
At ten months, the human parent will instinctually wish to return to the forest where they were impregnated. This journey can be challenging, and often pregnancies can be extended a few months in stasis as they navigate returning with such a large belly, though the increased musculature aids with this trek. When contact is made with the creature, both it and the human will go into labor.
Birthing the cubs inevitably has little to no risk involved. Labor takes upwards of three days, once proper contractions begin. During labor, it is most often seen that contact with the P. gremii lowers stress for both parties. In the majority of cases, P. gremii gives birth to its human offspring before the human parent begins to crown with the cub. It will then attend to the other parent, humming and providing assistance to the birthing human, often through massages. Cubs are born snout first, with the musteline-like head shape allowing for easy passage through the cervix.
Once both parents have fully birthed, they will spend some days together to recover (P. gremii will have stockpiled food prior to the birthing event). After which, the human will return to their society. Effects on the genetics of the human offspring have yet to be fully studied.
Lastly, the most vital reason this creature is sought out is due to a unique effect associated with the pregnancy. Humans who are at high risk from pregnancy, infertile, or otherwise face challenges with giving birth themselves, invariably have an easy and safe pregnancy with the creature's cubs. Carrying P. gremii in one's womb leads to a restorative effect, allowing them to healthily carry and birth their own subsequent babies.
Further research is needed to fully understand P. gremii and their effects on human pregnancy.