Legion: Cursed Dominance

There was only one thing Benji wanted and that was for his sister to be healthy and safe, this was why he became a hunter.
Years ago, some portals leading to the outside world cracked open, allowing monsters and creatures to invade the human's world. That same time, some humans awakened special abilities within them and they stood a chance against these intruders.
Benji never wanted to become a hunter but then he just had to do it because of the debts he had to clear and his sister's declining health. But then, he was just an E-rank hunter.
Luck shines in him and he was granted a short-term system that helped him become stronger by completing tasks but unfortunately, something terrible happens and he looses his life.
But was it supposed to be his end?
No, it wasn't.
Then it awoke in him, something from the deepest part of hell — Legion.
An ancient devil known for being merciless and evil. A malevolent being whose aim is to sit on the pinnacle of the world's destruction.
Can Benji control this dark force? Or will he let it consume him?.