The protagonist is raised by ascetic wizard-warriors and sent to a city that is avowedly evil. We get explicit detail of the torture, murder, cannibalism, and other disgusting crimes happening there. He's horrified by what he sees, but turns to the dark side after he spies on the wife of his dude-bro best friend (a barbarian warrior) as she has sex with another woman. Yes, that's right, watching two women perform cunnilingus flips him from a horrified observer of brutality, cruelty, and murder into someone who is literally willing to cut off someone's face to wear as a mask.
I bought a copy of this from author Mark Rogers at Lunacon back in 1989, because I really enjoyed his Samurai Cat parodies. After hearing him talk about his writing, and reading these books, it's clear that this guy suffers from homophobia so profound it qualifies as a derangement.
If you want to read fantasy action mixed with torture porn and deep discomfort with sex and/or 'so bad it's good' gone very bad, these two books are for you. Otherwise, you probably don't floss your teeth enough, so why not take care of that now, while it's on your mind?