What is more terrifying?

Okay, then you came to the Black (white, red, green) Dragon as a Wizard, and not just any dragon, but specifically that one!:)
Not many, I counted 4.
Oh dear... how uncouth of you. Very bad!..

And why is that?:)
I think so.:)
It depends on how you look at necromancy; essentially, it's not magic, but the ability to control and raise the undead. Perhaps it's an innate ability.
Or maybe there was a god who raised the first undead lord and subsequently endowed chosen ones with this gift.
And why didn't the Wizard look for ways to achieve immortality without death? After all, it's unpleasant, and it also takes energy to maintain oneself in the form of a corpse. It's not for nothing that life doesn't leave it; it's held by will and energy.

as an option - to inhabit a foolish mortal.
and Smoke didn't just want to eat, but also to rob, kill, and defile girls.

Where does so much energy come from to inhabit a mortal? So, a whole bunch of it was spent on appearing on the main level.
And it's unlikely that it's so easy to inhabit the soul of a foolish mortal. Even powerful demons, summoned by inept Wizards who lost control, could only tear the summoner to pieces and roam free for a while.
He didn't really need to rob; he had enough. It's unlikely that the dragon was interested in human girls. He only killed out of paranoia, all the travelers passing by.

killing and robbing anyone - be it a person or a cockroach - is bad, and they also kill good people.

Good Dragons are also killed. C'est la vie.
What's so bad about that?

...and even defenseless peasants...

Oh, the horror!:rolleyes: