I Contracted with the Devil and Became the God of Wizards

(Western fantasy, wizard, knight, fighting spirit, magic, dragon, goblin, goblin, vampire, god...) I was stabbed in the back by my brother at the beginning, so I could only take a letter of introduction from the Wizard Tower to become a wizard apprentice. However, I was coerced by the evil demon on the way and had to submit and sign a contract. I could only make a living by doing bad things. I really don't want to do bad things!