Transmigrating into the world of Harry Potter as a... symbiotic Obscurial, Vale would come to realise how tricky his situation was. Belatedly being able to analyze his own, difficult-to-control abilities yet terrifying raw power, he would have to navigate the world with a sharp, deceptive mind.
It was inevitable that he would be a glass cannon. Therefore, he needed a way to remedy his shortcomings — and fast.
This story has a lot of potential. Hope mc has no morals and seeks power and immortality