I'm adding these two Wikipedia articles to the lists of things I wish I'd read a year ago..

[alexandraerin]

Malignant narcissism:

The malignant narcissist is presented as pathologically grandiose, lacking in conscience and behavioral regulation with characteristic demonstrations of joyful cruelty and sadism".

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Malignant narcissists, in contrast to psychopaths, are also said to be capable of developing "some identification with other powerful idealized figures as part of a cohesive 'gang'...which permits at least some loyalty and good object relations to be internalized". "Some of them may present rationalized antisocial behavior - for example, as leaders of sadistic gangs or terrorist groups...with the capacity for loyalty to their own comrades".

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Typically in the analysis of the malignant narcissist, "the patient attempts to triumph over the analyst by destroying the analysis and himself or herself".

Narcissistic supply:

The term narcissistic supply was employed by psychoanalyst Otto Kernberg as part of his description of what he called the malignant narcissist. Kernberg referred to the coldness in a such narcissist's relationships as the "tendency to disregard others except in temporary idealization of narcissistic supply" and he suggested that this was a feature which distinguished pathological from normal narcissism.

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Those who are providers of narcissistic supply may find themselves being treated as if they are a part of the narcissist. "In the mind of a narcissist, there is no boundary between self and other."

Edit: Note, this is not an attempt to diagnose anyone with anything, especially as neither term is an actual diagnosis. But they refer to and describe patterns of behavior that can be hard to spot when one is enmeshed/immersed in a situation, so having them pointed out or described can be helpful.