No one really knew how long Dusk Manor had been abandoned on the hill overlooking the town. Some said as little as twenty years. Others said as much as three hundred. Whatever the time length, it was unanimously agreed that one day, it had just shown up. But it was odd, because the townsfolk knew it had been there a long time. It's like you get to know someone in your junior year of high school and they tell you that you two have had all the same classes and teachers since kindergarten. In whatever case, Dusk Manor stood on the hill, undisturbed since it's abandonment. It reminded the townsfolk of the infamous Hill House from Shirley Jackson's novel.
But this was no ordinary manor. Dusk Manor thrived with life, but not in the way you might think. That is, the house itself was alive. If the townsfolk had known this fact, they probably would have torched it to the ground years ago. It looked like any other large mansion, with it's ornate windows, many chimneys, wings, floors, conservatories, and rooms, but it was all alive none the same. The townsfolk were wrong: it HAD just appeared one day, and it had remained empty as it had the day it appeared (which was, in fact, just one hundred and twelve years ago). Whatever alien power the mansion had warped the minds of the townsfolk to accept that it had always been there.
Most mansions like this were probably haunted, full of the run-of-the-mill ghouls, ghosts, and beasts, waiting to scare the shit out of any unlucky teenager who wandered in on a dare. But Dusk Manor was no ordinary mansion. Sure, it had it's beasts, it's ghouls, and it's goblins. But it only had one thing in mind: to transform. It made sure that any living thing that entered it's doors did not leave until it had endured some kind of transformation, whether it be full animal, half-animal, anthro, sex, weight, body parts, hair or eye color, real or imaginary. And it kept you at the same age, so you could be in the house for as long as it took... possibly forever. If you were lucky, you got out with just a change in hair or eye color. If you were very unlucky you became some kind of Eldritch abomination that would remain in the house as long as it stood, transforming others as the things in the house and the house itself had transformed you. There was no limit to how many times you changed or what you became, but as soon as you had changed, even a little bit, and stepped back outside, the changers were permanent and you could never step foot in the house again.
It had pacified itself over the years by capturing stray dogs and cats, mice, bugs, birds, and one human (he had been transformed into a deer and ran off into the woods surrounding the town, where he was shot two weeks later by a hunter), but it had had enough. It was tired of trying to capture victims the natural way: the thrill of exploring an abandoned house had been replaced by movie theaters, smartphones, and television. So it sent out a call, an idea that planted itself in someone's mind, to finally check out the old house on the hill.
It is stormy tonight. Black thunderheads cover the sky like a blanket. Purplish-white lighting crack across the clouds every few minutes. Rain pelts down in sheets. The lighting illuminates the weed and grass-choked hill the mansion stands on, and the dark figures climbing it, making their ascent to the huge front doors of the house, where it stands, patiently waiting.