For thousands of years, scientists have heard about dreams and how they sometimes affect people or change their lives, but they never understood how it worked, they had many hypotheses and theories but without proof, it is only mere conjecture and not worth anything. Yes, some people have done research and published papers on how it might work, and they got universal praise back in the day, but today's world scientists want to take it an extra step further. Now they think they may have had a breakthrough moment. They made an examination table with a helmet at the end, and the helmet is placed on the subject's head, it turns the brainwaves into electrical signals, and it goes through wires and cables to two monitors, one of them shows what the subject sees in the dream world and the other shows both the dream world and the test subject’s spiritual/soul/dream body from a third-person view.
The Scientists post a reward for $1 Trillion for anyone who volunteers to be a test subject for their new device. The reward is genuine but only if you survive the experiments without getting transformed. Most people believe this offer is too good to be true, so they do not sign up for it. But you really need a lot of money and very soon too. So, you sign up.
You go to the Dreams and how they affect people wing of the research building and the Scientists welcome you. They explain that they have always been fascinated by dreams and how they might affect a person in the real world and that with your help, they might be able to see the results for real. First, they ask you to strip naked, lie down on the examination table and put your head in the helmet so that they can see the dream world that you see in your dreams. You have to strip naked because the machine can't conduct any research if you are wearing any clothes. You do so and you go to the Dream World. As you do so they monitor your physical body, your blood pressure, heart rate, ekg, eeg, breathing and all your other vital signs. They are also see the world from your eyes thanks to the helmet transforming the brainwaves it receives into electrical signals and putting them on one of the monitors while the other monitor shows both the dream world and your naked dream/spiritual/soul body from a third-person view.
As you are in the Dream World you hear a voice that you must go through some trials in the Dream World before you can go back to the Real World, but if anything happens to your Soul/Spirit/Conscious/Dream self here. It will affect your real/physical/waking world/human world body in the other world. For example, if you are male and you get milked by a milking machine, your scrotum and penis will turn into an udder and teats or if you are female and do not have a scrotum and penis, you will just grow an udder and teats on your crotch. If an animal gets you, you will turn into a female version of what animal got you complete with tail. If you succumb to Water, you will become a marine creature. Mythological creatures can turn you into their female brides. etc.
This is a very dangerous assignment, and you might lose your HUMAN LIFE if you are not careful and become something else entirely. But you have to do it.