Trust but verify

You stare blankly at the ring for a while before chuckling to yourself and shaking your head. "Really? You repeatedly threw yourself randomly through time and space with no destination in mind other than hoping to find someone interesting?"

"Pretty much." The voice in the ring says, chuckling along with you. "Remember, I'm immortal. Not many things can harm me, and I'm going to be traveling around forever. What I'm most afraid of isn't danger; it's boredom."

You shake your head at the ridiculousness of all this. "Look, I'm in way over my head here. Everything you've said so far has been the most incredible thing I've ever heard, with implications that I'm not really equipped to understand. I'm sure someone smarter than me would know exactly what questions to ask, but I'm too overwhelmed to think about what those questions might be. I do know that if what you're saying is true I definitely want in. Trading control of my body during the time when I'd just be asleep anyway in exchange for actual superpowers is a great deal. The only thing holding me back is the fear that maybe... you're completely full of shit."

"Don't get me wrong, you seem like a nice enough dragon, and my gut tells me you're on the level, but you could just as easily be making this all up to trick me into giving you my body. And if I do that, maybe I fall asleep and wake up to find my life in shambles. Or, even worse, maybe I never wake up at all. So, rather than spending a bunch of effort trying to sus this out the hard way, let me just ask this: do you, you know, do you actually need my consent to take over my body? Like, is there some kind of magical restriction physically preventing you from taking me over if I don't agree?"

"No..." The voice in the ring admits. "I could take over an unwilling host if I chose to; however, I prefer not to do that to someone without their consent. I have a strong respect for feedom and body autonomy."

"Okay, so, for the sake of easing my mind, would you mind demonstrating real quick? You know, take over my body for a few seconds without me actually giving my consent?" You ask. "I figure, if you really can take over my body without me signing anything away, that will at least prove that you don't really need my consent, which means you probably aren't just trying to trick me into giving it... Does that make sense?"

"Sure." The voice in the ring agrees. "Are you ready?"

You nod, and suddenly a feeling of vertigo overwhelms you. Your senses still work, and you can still feel your body, but at the same time you are no longer able to purposely do anything. All the tiny, little, almost subconscious movements you were deliberately making to sit up straight are no longer under your active control. You watch as your own right hand raises up and waves in front of your face.

You are no longer in control of your body.