My ex husband is a narcissist. It took me years to accept and not blame myself for everything toxic he did, all kinds of lies, manipulation and abuse. I agree with BlessedArt that NPD is a diagnosis and I also agree very few people who are narcissists would allow themselves to be diagnosed, or even think they needed it.
The scary and, I guess in some ways, "good" thing is that there IS a commonality and pattern to how they ostracize their targets. My ex did it with my children and with their teachers. My son is on the autism spectrum and he did it with psychiatrists, doctors, everyone. It was a living hell until we were finally in litigation and through discovery I was able to see all the lies, in writing. Sounds like a Lifetime movie I know.
These people, more men than women, thrive off other people's pain, usually good people who are highly empathic. While I would need a diagnosis to believe what a lot of people say about particular behavior patterns, I don't need it with him. And after 30 years of pain for others, he still believes everyone else is the problem.
I've moved on and I'm discharging this energy from my body but what a trip it's been.