Gaslighting is a difficult aspect of emotional health. Probably the most common and easiest way to think about gaslighting is when you are psychologically manipulated by someone to question your own sanity.
When the abuser can't directly inflict abuse upon his victim, he may find accomplices to do his dirty work. Abusers often use other people to do their dirty work for them; the abuser's social milieu, the victim's social milieu, the System
Abusive relationships are complex situations which take a lot of courage to leave. When a survivor leaves an abusive relationship, the perpetrator's sense of power and control is threatened, and this may cause the abuser to retaliate.
That is why leaving is one of the most dangerous things a survivor can do.