Is he evil or just degenerate?
VERY evil. Think of it as a Sukuna level of evil, he will do anything he sees fit to achieve what he wants and doesn't care about "morals" one bit. Sex just happens to occasionally be the most convenient option, so he goes with it.
Will there be a harem?
Yes! And it's full of girls with actual character. There won't be a lot of girls in the harem though, because girls don't just look at an evil wizard sacrificing children and say "I love him."
There will be minor female secondary characters who get action scenes too, but the main harem will be very small.
A fun fact, another reason the harem is small is that the first heroine and other prominent members are Yanderes, and I MEAN it. Because the MC is evil, his girls are too to some degree, so expect a culling game between harem members.
Author's Note
Originally I had planned to write a full smut story, but after thinking it through, the MC's personality is too interesting for it to just turn into a sex-driven story. So expect a rough beginning that transitions around chapter 30.
What is the MC's name?
Just read the story, it's revealed at the end of Book 1. Any names before that are just the bodies he's been hopping through.