What do Narcissists and borderlines have in common?

There is a reason why so many toxic and co-dependent relationships include a narcissistic man and a borderline woman. While at first glance these two individuals have very little in common, they share some fundamental characteristics that can be uncovered if we look very deep below the surface.
Both, narcissistic personality disorder and borderline personality disorder are part of the Cluster B in the DSM classification. That by itself indicates that there must be something they have share, even if those qualities are present in fragments. What could they be? Well, they both share an underlying feeling of depression, a strong fear of abandonment and chronic feelings of emptiness.
You would never say that narcissists know anything about depression is or that they experience emptiness, yet deep down they do feel depressed and empty as they strongly believe that they are not lovable nor good enough. That is why they need so much admiration and praise from other people. It gives them a sense of existence, of being worthy. Borderlines, too, feel depressed and empty but prefer to fill that void by establishing relationships. They don't seek undivided love and admiration from others, it is what they want to provide. Borderlines can't live without being in a relationship, narcissists can't live without the narcissistic fuel provided by other people. In theory, this would make them a perfect match. Unfortunately, narcissists can't cope with the borderlines' desire for intimacy.
This is how it happens: at first, all is great. Borderlines provide narcissists with love, admiration, devotion, which fills the narcissists' void. Since borderlines feel the depression and emptiness of narcissists and know how horrible that feels, they try to make it better. By making it better for them, they make it better for themselves as well. Narcissists on the other hand provide a seemingly stable person on which borderlines think they can rely, as initially, narcissists present a charming, reliable and strong front. There is nothing a narcissist can't do! However, things start to get complicated when borderlines want more intimacy, as the logical next step in their relationship. This is where the fear of abandonment comes into play. They both experience it, borderlines more overtly, narcissists deep down. The more intimacy the borderlines wants, and there can never be enough of it, the more the narcissists start to withdraw, as it gets too much for them. They fear the borderlines might uncover their true nature, the one they are so desperately trying to hide behind the narcissistic mask - the vulnerable, unworthy, unlovable self they believe to be. And should they ever uncover it, they would leave them, which narcissists are trying to avoid. Borderlines, sadly, understand the withdrawal of narcissists are abandonment and will do whatever it takes to prevent it. The power struggle who will leave whom begins, first as a testing phase. Borderlines become obnoxious in their behavior as they test how much narcissists love them. How far can they go before the narcissist leaves? Narcissists withdraw and disappear, only to return, to check whether the borderline is still willing to take them back, because when the relationship was good, their emotional needs were fulfilled completely, even those they had no idea they had. They also feel a rush of positive energy of seeing the borderline crawl for their attention, begging them not to leave. It gives them an immense sense of importance and power. It also frightens them on some level because if this crazy borderline groveling person loves them, there must be something wrong with the narcissist as well, right?
See, there is negative mirroring going on in this kind of a relationship. Both partners share the depression, fear of abandonment, desire for being loved and fearing it at the same time, an unstable sense of self that must be provided by the other. Until both resolve the past wounds and script patterns, they will always push all the wrong buttons in each other, which will inevitably lead to hurt, pain and suffering. Therefore, couples' therapy is the best solution for them as they need to understand which painful experiences brought them together in the first place.