You may not be the smartest guy in the world, but with the kind of power you've got, it shouldn't be too difficult to plan your way out of this prison.
"Everything alright in there?" The guard asks, coming into your room.
"Absolutely, officer. Everything is just peachy." You answer, sitting patiently in your bed. You don't have any need to worry; you'll spring your plan into action tomorrow.
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The next day, 10am.
"Hello? Good morning?" The guard asks, opening your door and seeing that the light was shut off. He points his flashlight over at your bed. "Oh... you're still asleep." He whispers to himself. "I guess I'll just... leave then." But before he can reach for the door, he finds his clothes are becoming loose-fitting. Just a few moments later, the guard loses all of his physical form, descending onto the floor in a pile of clothing.
You're pretty sure this is following the rules of the ring so far. You wished your pillow to become the shape of what your body looks like laying down. Then you waited in the darkness for someone to come in, and then you, well...
You reach into the uniform and pull out a plastic doll. It's a naked boy doll like what an elementary school-aged girl would play with. You get undressed and quickly put on the guard's uniform, stuffing the transformed guard himself in your back pocket. He is still alive as a doll; you didn't want to end his consciousness. You decided also to be courteous and let him maintain a relatively humanoid figure, despite how much easier he would be to hide if you'd turned him into a paperclip or something.
You make haste in exiting the room and acting like you're carrying on with business as usual. You breathe a deep sigh of relief, having finally escaped that room. You might almost be free, now. You're not in the clear yet, however. If they realize you're an inmate, you might be dead immediately. You have to survive for at least another hour.
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Through sheer luck, your fake patrolling looks just legitimate enough to not draw any suspicion, and no one asks to see your back pocket. Another hour has passed, and you've got to make a decision about what to transform next. It's very unlikely you'll continue to get away unnoticed much longer. This next transformation could be life or death!