If you're into the strange and unusual then you've probably heard about the mysterious disappearances of people over the years. No one, besides the people themselves of course, knows what happens to them. You're about to become one of the people who know what happens because you are about to disappear.
You don't quite know this yet but a long time ago when magic was accepted and there were powerful magic users a witch created a magical tower for some amusement. She had planned on having the tower transform people who entered it and then let them go after reversing the changes. However her spell was interrupted by a knight, who believed he was doing right, thrusting his sword through her heart. As a result the tower disappeared and that was thought to be the end of it. However it was just the beginning as the disappearances started happening soon after. For you see the tower still existed but was now hidden and at random times opens a portal to itself around the world. Of course most people don't see the portal when it opens and they get a shock finding themselves inside the entrance of the tower.
They soon find that the tower has the ability to transform anyone into anything that can possibly be imagined. Many of those that have been stuck inside the tower for years have formed little communities on the different floors, mostly along the lines of what they were transformed into though there are some different transformations within them. It isn't only once that someone is transformed but they are transformed over and over at different times so one day a person could be a boy and the next hour be a pair of panties then wait anywhere from minutes to years to be transformed again.
Of course there is a way out of the tower but few manage to find it and those that do are rarely transformed back into their old selves and if they are they're so traumatized by what has happened to them that they can't tell anyone what happened. After someone finds their way out the tower changes the exit so that exit can't be used again for a long time.