If the relationship ended, he/she would have set the scene for it to end. They fear abandonment but push and pull so much the non-narcissist can not play any longer. He/she will function by simply replacing you. They wont let you 'go' in their heads. If a true narcissist they will absolutely feel that they were / are better than you, and they are charming to a fault (they are able to act that way when it suits!). So it is only a matter of time that they bounce into another relationship They will unceremoniously discard you, and that is a bitter pill to swallow.
If you truly believe that you have been with someone you believe displayed narcissistic traits, you will have put up with all sorts of hellish behaviour to get back what you had in the beginning. You would have seen glimpses of it in between the rages / silent treatment: you would have believed once they had gotten over yet another issue in their life that all would be good.
However, if you are the narcissist, well done you for recognising you've some issues. It may be possible that someone you were with has made you believe that you displayed traits that are narcissistic. The issue here is that if you think you are, chances are you are not. If you are questioningour behaviour, best get some help.
If you have separated from someone you believed had narcissistic traits, please do see someone. Cognitive behavioral therapy helps people who have been in abusive relationships. You are not to blame, but the help does assist you questioning why you would accept such bad behavior and help you find yourself again.
Finally, to answer your question there are many ways that they function if a true narcissist. They will reinvented themselves on all levels. They may change their style, their values, i have heard even their religion. They will put on the charm offensive to become the perfect fit for their next source of supply. They may also become vindictive, manipulative, play the 'victim', but what they do more often t not is to have a scapegoat for their problems. They are never to blame FOR ANYTHING. They will give their version of events that are vastly so very different from how you saw such an event or anyone else for that matter. And they will lie. Because they can not and will not accept any portion of blame. We can all look back a failed relationship and take a portion of blame, unless you are narcissist. All these bad things (ie manipulation, lies, vindictiveness, threat cold-calculated abuse) come when they know that they have lost for good. IF, however, there is an inkling of a way back in (and to their comfort zone!) they will lay on the charm offensive to win you back. Once fallen the relationship will revert back to the status quo where you were unhappy. Is this what you were asking?
I am certainly no expert. But over the last 19 months I have read anything and everything I can to assist my recuperation after a long-term relationship ended with someone who showed every trait of Narcissism. I am a well educated person and by taking such steps by reading as much as I could, I have helped my way through some very tough times and although the tough times are still ongoing, I have educated myself to help ME.
Books that have helped me, and may help you are:
Narcsisstic lovers (Zyan)
Stop Walking on Eggshells
How to deal with manipulative people
And endless internet searches on Narcissism, loads from Sam VANKIN...
Hops this helps x
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