AS THE WITCH SAYS

As the Witch Says summary:

In a world where magic and might clash, Isoc dreams of becoming a wizard despite his muscular build. Raised by Father Kay, a priest who insists he become a fighter, Isoc faces constant pressure to follow a path he doesn't desire.
Desperate to pursue his magical aspirations, Isoc ventures into the treacherous Dark Forest. There, he's attacked and nearly killed by a curse-eaten monster. At the brink of death, he's saved by a mysterious figure known only as the Witch.
However, salvation comes at a price. The Witch, seeing potential in Isoc, forcefully binds him into a magical contract. "I'll give you a curse, so make a contract with me!" she declares, insisting that Isoc now owes her his life.