The ability to rip people's souls out once they're weakened enough and eat them to increase my overall mental and physical health and strength (though not to the point where I'm so intelligent I forget how to breathe or so strong I can't move and over such horrible ironic fates).
The ability to survive in any environment without being destroyed, such as the vacuum of space, the crushing depths of the sea, etc.
Immortality with my physical appearance halting at 21 and my body regenerating any damage it takes.
So, power number one would work with power number 3 to get me back into working condition in a combat situation, as well as helping me gain power and experience.
Much like in an awesome video game!
"Nom-nom-nom! Soul is delicious!"