It takes two to tango -- and an equal number to sustain a long-term abusive relationship. The abuser and the abused form a bond, a dynamic, and a dependence. Expressions such as "folie a deux" and the "Stockholm Syndrome" capture facets -- two of a myriad -- of this danse macabre. It often ends fatally. It is always an excruciatingly painful affair.
(From the book "Malignant Self-love: Narcissism Revisited" by Sam Vaknin - Click on this link to purchase the print book, or 16 e-books, or 3 DVDs with 16 hours of video lectures on narcissists, psychopaths, and abuse in relationships: http://www.narcissistic-abuse.com/the...)