The concept is based around the idea of the book and movie, The Golden Compass, where everyone has a Daemon that is born with them and takes on characteristics of themselves. This is mixed with the book series, The Familiars, where different types of animals all exhibit different types of powers.
Each Daemon is a type of animal that shows something deep about that person's soul and is completely random until that person matures into an adult where they will stop shifting forms and take their final appearance.
Familiars can all exhibit different abilities like a certain type of cat can become invisible or a bird can carry 20 times there weight. Each one varies and is up to the author to determine what each animal's ability is.
The concept that I am speaking of is a mic of the two books. People are born with Daemons that shift in form until there final stage at adulthood. Daemons have inbuilt abilities that are unique to each form that they take (Example; black cat equals telekinesis). Daemons that can still shift get weaker versions of each ability, but once they reach adulthood and take their final form they get far greater power with the ability earned.
You as an author can create a story around this in any fashion I just thought it would be an interesting read. (Sidenote: you can totally make a class system around the final Daemon form you achieve with those with lesser combat ability on the bottom and those with greater on the top)