You stared at Ozzy, confused and somewhat scared as the shock was leaving and the gravity of the situation was settling in. "I.. I don't know what you're expecting of me. I'm not a fighter, or even an athlete. Magic doesn't exist where I come from and I probably failed my calculus exam due to not showing up! The police are probably looking for me. My parents are surely scared to death. ..."
As you fell into incoherent babbling and continued getting more worked up, Ozzy smiled empathetically, "Be at peace, little one."
The collar activated and quickly dulled your thoughts. Though the emotions behind the thoughts were strong, and unlike controlling your physical actions, suppressing your thoughts took time. After a moment or two you looked at Ozzy, smiled, let him know you were better, and thanked him for keeping you from getting hysterical.
Ozzy smiled comfortingly, "I can see your body is not a tool in your 'calculus' trade. Though I have a suspicion of what you are, this is an easier test than expending spell materials that would take several days to replenish. I believe you are unique in that you can specialize yourself to fill any task you are given. I believe that if I hadn't used the collar yesterday while coming home, your innate abilities would have kicked in making the task easier for you." Ozzy motioned for you to step to the two handed great-sword he had conjured moments ago.
You reached down to lift the sword and realized how huge it was. It was a constant strain to keep it in the air, after all it was five feet long.
Ozzy piped up, "Yes, now, I want you to close your eyes and think of a creature that can wield that weapon with ease, focus on that creature. Imagine being that creature, and when ready, try to swing the sword."
You didn't know anyone strong enough to use a sword like this and reasoned that it could only be used by a mountain of a man. Your brain quickly put together that you did know a mountain, The Mountain from Game of Thrones! As hard as you thought you couldn't picture his face, you brain could only picture that of Jon Snow as you were several seasons behind and would never catch up after that scene of betrayal at the wall in the north. Despite the setback you imagined being... the snow capped mountain, and swung the sword with all of your might.
At which point you lost control, spun in circles, and fell to the ground. Ozzy let out a triumphant laugh and when you opened your eyes you saw him grinning at you like a fool. "Yes, yes. You got me to make a fool of myself, but this will never work, I'm nothing special." You grunted as you rolled to all fours and stood up awkwardly. That fall was oddly disorienting, and you cleared your throat as your voice sounded much deeper.
Ozzy looked at you perplexed for a moment and then pulled his wand tracing it in a huge circle and mumbling some sort of incantation. Though you felt no draw of power a few seconds later the large and imposing figure of the mountain appeared with Jon's black hair, and young face complete with his beard just as you had imagined. You reasoned that Ozzy pulled the image from your mind through the familiar connection and wanted you to try again. You were careful not to move or show any inkling as to your assumptions, why he would be SO familiar with that spell. A spell that showed life sized images of what you were thinking of. A spell he used so much that he would drain no power from you.
A second later Ozzy stepped out next to the mind portal and made a very pleased gesture motioning to the portal and back at you. "Ozzy, it's not working, I'm not what you want me to be." Ozzy again looked very confused and stepped in front of the mind portal, and much to your surprise, his reflection appeared.
Suddenly the realization hit you that the spell isn't a mind portal, but a mirror. "The reflector spell appears to be working for me, can you not see it? Ooh! Are you immune to illusory magics among all your other gifts?" he asked excitedly. "A familiar with shape-shifting and true seeing could only be a blessing from the gods!"
With an overwhelming mix of horror and excitement you examine every inch of yourself that you can before the spell winks out. When it does you caress your muscles, feel your face and newfound ability to grow a beard, and examine your now long, black and curly hair.
(As "you" are just coming into your powers I think it's important to note. To everyone's knowledge, you have only ever been, or at least only have memory of being a bipedal human. So moving around via flight, fins, or four legs will surely take getting use to and be an issue worth addressing if you go that route.)