Shame is a core sense of feeling unworthy, inadequate, not good enough, deeply flawed, or "less than." It is an internal state that arises from failing to live up to our expectations or the expectations placed on us by others.
Shame plays a huge role in narcissistic abuse. Deep-seated and hidden shame may be the primary drivers for toxic behaviors. Narcissists disguise their feelings of shame with displays of grandiosity and seeming superiority. They use techniques such as blame shifting and projection to disavow their shortcomings, flaws, and faults and dump them onto others, thereby disowning them and leaving you holding the bag. (The "I'm rubber, you're glue" defense.) These actions are a cover-up for their unacknowledged feelings of unworthiness.
The narcissist transfers their shortcomings and shame onto their victims by making them feel inadequate and flawed. The victim of narcissistic abuse begins to experience their own sense of shame—which explains why narcissistic relationships leave their victims feeling so unworthy.
While the narcissist will never claim nor admit their feelings of shame, our task as survivors is to face our own feelings of unworthiness so we can heal from within—and so that we no longer accept the deflected shame of others.