Narcissistic Personality Disorder – a disorder of the self. When they don't have their own self, they need another person self to survive.
Donald Winnicott coined the term “false self” to account for the carefully designed persona that most narcissists put out into the world. This is not an authentic expression of self—it’s a costume or disguise.
“Narcissism takes many forms, but many narcissistic acts take the form of embroiling another person in petty, tedious squabbles that distract others from their feelings, goals, values, and guiding principles. Narcissists compulsively seek out mastery, victory, dominance, and superiority in order to prevent encounters with pain, vulnerability, and inadequacy. When spending time with others who are their equals or superiors, narcissists can be overcome with envy, triggering a compulsive focus on dragging others down. It’s a dynamic of competition—a zero-sum game.”
Spending long periods with a narcissist has quite a negative impact on an individual and breaking away from one is sole tearing. A lot of self-reflection and self-healing is needed to recover and remember who you are and not who they made you out to be.