I've got an idea for a character, we'll call him Jack for now, but you're gonna need to OK his backstory and ability as they are both potentially issues.

For backstory, I wanted Jack to be someone who was recruited into those scientific fields you mention as a child. When the story starts, he would be at an age range that would be this universes equivalent of one's early twenties. I would like for him to be working as a researcher apart of a team that is trying to learn the secrets of AMA (one of many research groups headed by various Noble leaders). His team in particular would work out of the AMA storage facility that is destroyed. The team would be a group of six people around the same age as Jack, and one supervisor. I would like for one of the team members to make a small discovery that would allow the research team to get a glimpse of how AMA works. The entire group is told about this discovery, but the physical information is destroyed in the explosion, and most of the team members are killed. 

Now, depending on how getting magical powers works and whether or not you'll let Jack's ability fly, I would like for four or five members of the team to survive the explosion, but for most of them to be assassinated (if this doesn't fly, then just two survivors other than Jack) by the people who destroyed the facility. Jack will be killed during the actual explosion, but the ability that Jack gains is for his consciousness to flee to another host after the body it resides in dies. Tier 1 would make it so this process is completely random, allowing his consciousness to take over animals and people at random and anywhere within a multi-mile radius. I would have him be trapped inside a nobleman at first, who ends up being assassinated along with the other surviving team members (Jack attempts to find the team members and learn what's going on, which gives him away), then a rat (which is crushed in some machinery soon after Jack enter its body), and then a citizen, which is where we will start with him. 

The way this ability would work is that he can only enter the body of an animal or person whose mental defenses are completely lowered. A mind with a lot of stress on it would reject Jack's consciousness, as would one that is aware of Jack's presence. As it is right now, Jack would not be able to enter the mind of someone who has magical abilities like his own. 

I came up with all of this minutes ago, so I'll leave you with this to OK or pan before I go too crazy. I plan on expanding on the rules of this ability and Jack's backstory more as I continue working with this character, but right now I think you have enough to get a general idea. The issues I mentioned earlier are that you would need to give me a little bit of information to make Jack's knowledge worth killing over, as well as the fact that currently Jack's ability makes his conscious mind immortal (at least early on in the story). 

Sorry for inconsistencies or grammatical errors in this post. I haven't done much in the way of creative writing for a couple years now.

Also, Jack is just a placeholder name.