Let's try this:
Name: Essence
Age/gender: 15, Male
Race (feel free to make it up): Spirit (bodies made up of pure energy which can solidify)
Element:
Appearance: when not solidified, Essence is similar to a flame, although it can roughly shape itself into something (for example, he might shape itself into a human figure and take the general appearance of a human which looks like it's burning in a blue-ish flame). When solidified, can take any appearance, as long as the energy he has is enough energy to convert it into mass (at 15, they have a crazy-ass amount of energy on them, but it is just enough to take the appearance of a 8/9 years old human boy).
Personality: he is respectful but for that he sometimes looks cold, expecially when he talks to people looking like a little kid. He's rebellious due to his family.
Bio (optional): he's the second son of the royal family from his planet. On his planet, the king and the queen are chosen based on their strength and their abilities and their main objective giving birth to a Prince. The first son of a couple is always stronger than both of his parents, and, for that reason, the Prince is the strongest from their planet. It's easy to assume that the Prince we'll never be killed due to being the strongest of its planet, and that he/she'll easily become the king/queen for the next generation. The other children of a couple are instead a lot less powerful, but if they inherit the right traits, they can become royal guards. Of course, not being the first son means that, other from not being as strong as the first son, he may have some weak points, although he didn't have a chance to find them yet.
Essence was found to be strong enough to become a royal guard, but he rebelled against his parents' decision and decided to go to the Quantum Academy instead.
Class (if teacher): n/a