The Casper-3

The Casper-3 is a powder once consumed. The person who has consumed it may revive anyone they want in their life. In a place where animals and humans work together to defeat the negatives.
All people and animals are born with one or two of four elements: fire, water, earth, and air, called light energy. Once someone has graduated high school, they may go onto the Academy of Tamers (or a post-secondary institution to get a job). Within the Academy of, Tamers, students may merge with an animal of their choosing with a weapon of their choice. In doing so, a person may be able to go and kill negatives. Negatives are dark energy composed into human form. They are created when a soul of a human from the Academy of Tamers has died, and their light energy goes dark.
In this world, one religion rules over the four main islands; however, each of the different islands interprets the religions differently.
Our Protagonist, Xylem, Will have to come out of his small village to the entire world to hunt down and find the Casper.