"The power is not really corrupting me yet, so when does it begin?"

Is what you would think to yourself.

As you live in a world of Dragons, Knights, Hero and villians, magic and runes. One main thing that sets apart one another is the magic one uses. Some go for fungal or fauna magics, while other go for more elemental magics or no magic at all, opting for physical enhancements, though being a hybrid is optional, one side is more romanticized than the other, being magic, mages, witches and wizards so hybrids are far and few between.

But for you specifically, you took hold of, 'The dark forces' for magic uses, which stacks upon your natural magic affinities and output/amount of magical energy. This 'Dark force' being a dark tome which you luckily got off of a dead demon in a peculiar disheveled gravesite.

With said tome and the essence of the demon which you got forcibly used as a vessle for the energy, which mixed basically perfectly with you. This provided great power and the works. But others, being the religious guru, or mages who don't see 'Dark energy' in a good light told you, and by whispers and boldly acclaimed to your face that you're definitely going to be corrupted and turned into a demonic entity, 'the new demon lord'.

But here you are, 100 years later, still fine with no corruption, you’re still the same self you’ve been for the past hundred years may be a bit younger because of the energy but that’s about it. Maybe a feature or two from the energy but that's easily reversible. Though maybe it's time after your hundred years of learning that you could do something new, perhaps take a few apprentices or anything you want.