How'd Morgan end up a child soldier in the first place? What was she fighting for?
Well, its not something he intended to happen at all in the first place.
For decades, humans had been fighting against demons. Originating from the underworld, demons are creatures that feed off the magic of humans. There are various levels of demon, ranging from 1 to 20, getting more strong and intelligent as they absorb more magic and go up the ranks. While a level one demon is around the size and intelligence of a racoon, At level 6, they have the intelligence of the average human, and the strength of a powerful sorcerer. At 20, they are nigh-omnipetent, and have more magic than whole armies. Demons are colonists, who have been attempting to invade the human world, to gather magic, get stronger, and conquer the land. That, alongside human-made destruction, has cause the world to become polluted and barren over time.
Morgan is a half-demon, child of a human woman and a demon who had disguised themself as human. Ever since a young age, Morgan had shown quite a lot of natural talent in magic, as many half-demons wind up having, but also a bit more control than average. Hell, the vision of them you see now isnt what they actually look like, but an illusion spell they've maintained since childhood to keep themself safe.
After an incident in a marketplace involving Morgan having to fight against a level 3 demon, her magical prowess wound up being noticed by the headmaster of Malgora Academy, one of the top magic schools in the country, who invited them to take the entrance exam. While a bit young for the academy, A year younger than other first year students (12) and without much training, she actually wound up passing and joined the school on scholarship!
As he was going through his years at school, though, the fight between demons and humans was ramping up. Demons ramped up collective efforts, beginning full on armed assults of cities and invasions of land. Humans declared full on war against the demons, the government vowing to push them all back to the underworld. As the war went on, It became more and more difficult for the government to get enough magically-skilled soldiers that could stand a chance against stronger demons. They pulled soldiers from universities at first, but began recruitment of students from magical academies soon after. Morgan was only 15 at this point, studying magic for only three years, but he was going to be forced to the front lines.