I had a very long term experience of it, with a co-worker who I was in a relationship with, as well (we were musicians in a band). It worked for a long time because I was so much younger than him when we met and I was all alone in the world. We had a family together and I couldn't escape because of it. He would say "If you leave you will never get the children, because you're crazy".
I did get the children when I left though, at least the youngest one's.
It taught me a lot about gaslighting.
He still tries to do it to our children, but, they are seeing through it more and more.
A few people came forward and told me things that he said about me, very damaging incriminating things. A social worker witnessed a lot if it and documented it.
I got some compensation for it, in the end, as well. Not a lot, the main thing was that it was vindicating, considering all I had been through.
A lot of it seemed to be motivated by envy and deep insecurity. And I made the mistake of correcting him, in front of other's, when he would publicly lie and claim credit for things other's had done.
In my case, when it wasn't working to scream at me that I'm crazy and put me down constantly and say very mean and unreasonable things quietly to get me upset around other's to claim my "instability" and "craziness", he turned to smearing me to everyone who gave him an audience.
It does backfire on them though. He is not well thought of by a lot of people in the village now, it seems. And I have someone, who has my back, that he is frightened of.
He also went to jail last year, for a short stint. Nothing to do with me though, other illegal activities caught up with him.
I am good at detecting narcissism now, because of him. I can read it in the media and politics. It becomes very obvious to read "the language of liars" when you become familiar enough with how it's done.
So I'm thankful for the opportunity to learn about deception and narcissism, because in the long run, it is advantageous to be able to recognise it early and create as much distance from people who are like that, as possible.
It did take a great toll on my mental health though.I think the triangulation can be the most insidious, damaging aspect of it. Particularly if they are able to hoodwink other's into believing incriminating lies about you. Very hard to deal with. It's good to have witnesses who can vouch for you, when that happens. And perhaps to document whatever is happening, just in case.