Imagine that you were part of a dragon race that was being ravaged by Thanos. As an attempt to preserve the race, the remaining dragons travel to earth to protect themselves using their magic to hide their true form; but due to hunting throughout centuries and enemies, they had gone extinct. Your parents try to save infant you by locking your draconic powers with their magic. Your father leaves you one of his scales, that harden to form a crystal, in order to lock your dragon blood. Your mother putting a spell above your neck in the shape of a birthmark, as a last act of defense, to ensure that your magic would not surface. Trying to mask your true form, they conjure an illusion that makes you look as if you are human. They abandon you and wait until you are found then adopted.
During a car accident (or any sort of physically traumatic experience), you are severely injured resulting in the crystal embedded within your body to glow. Your magic begins to strongly manifest itself regardless of the precautions by your parents. The Avengers come thinking you’re a mutant threat, but understand you’re confused and they offer to help you.
Thor returns to Earth with Loki, who comes as punishment for New York. Midst the Avengers reunion, Loki sarcastically chuckles asking how you got to get away with hiding your true form. Everyone finds out you have magical powers of some sort and it’s Loki’s job now to use his magic intelligence to unlock your true form and help teach you to control your powers.