My ex husband did this and still continues to this day. He lied to everyone about pretty much everything, big or small, throughout our entire relationship.
At one point in our marriage, we had a small business, had a great team working for us and a great friend circle. He managed to convince me that one by one, the staff and some of our closest friends, had confessed to him that they disliked me for various reasons, and so therefore, over time and to avoid conflict, I stopped trying to mix with them and removed myself from the day to day running of the business.
He told my father that I deliberately got pregnant with our third child, against his wishes.(Found out that little cracker from my parents, after we got divorced)
According to him, my father had molested me as a child (that's why I was never to be believed, cos I was mentally unstable.... conveniently), he told his family and many of our friends this juicy story, all absolute bollocks of course.
He had had cancer (numerous times).
Our second son was a result of me having an affair, despite the son in question being the absolute image of him.
His Mother suddenly had cancer, right when I said I wanted to separate. She oddly had no recollection of even seeing a doctor.
On one Valentine's Day, we had planned a romantic evening out, he got an unexpected call and he had to suddenly go back to his own country for his Grandmother's funeral. Found out years later, his poor old Granny happily survived to see another 4 Valentines, so where he went those four days, I'll never know.
He claimed more than once that his business partner(s) had all managed to rip him off over the years, taking his/our money, yet he 'forgave' them and continued their friendship, presumably cos he was such a loyal and understanding friend.
According to him, many, many young girls and women, fancied him, and indeed, my own Mother AND my best friend had tried to seduce him.
He claimed (and still does) to be close friends with anyone of any standing, such as Head Teachers, Doctors, Lawyers, Judges or local minor celebrities. He was fixated with sexual stuff and often told me and others, about other couples or individuals in our social circle who had either wanted to have threesomes with him or foursomes with us both. We were never engaged in anything like this and never discussed it, even as a private 'fantasy'.
He claimed to know a deep dark secret about most people.
And if anyone dies, has an accident, gets divorced, or gets in trouble, he claims to either be a part of the story, or know something mind-blowing about the person or people involved.
Once separated, he called the school, social services and the police on several different occasions, claiming my children were at risk, or that I had gone missing and left my then young children unattended. He ended up blatantly stalking me for 4 years, yet telling everyone, including police that it was of course ME stalking him.
We have been apart for twenty years and still he calls me to update me on our eldest son's behaviour as they now recently live together. Usually dramatically negative, all untrue and with no basis.
This person not only did a good job of ruining our lives, but upset his entire family who are very close and loving. Despite being called out, and offering support, he claims WE are the ones who are sad, bad and malicious. He casually forgot that mutual friends and relatives talk to each other, and the truth soon surfaces.
One good thing I did eventually find out is that his lies and manipulation going back over 40 years did NOT go unnoticed by others. Our friends and family, acquaintances and work colleagues were also subjected to his delusional behaviour, outrageous lies and seedy obsessions, and though he was allowed to carry on, in actual fact, most people played along because he is a likeable character and they couldn't be arsed with the drama of challenging him. I wished then that they had called him out as it would have perhaps led to me seeing I was being manipulated and not just batshit crazy ( or 'imagining' it) . Gaslighting at that level is seriously damaging and as a result can leave quite long term fears.
But, people are good at minding their own business and avoiding conflict, but I'll bet most compulsive liars are surrounded by people who would just rather keep their mouths shut than fuel any drama. Even now, despite knowing all I know, I still play along and then immediately erase everything he says. It's a sickness that sadly won't go away so proceed with caution.