There are evil people (by Peck's definition) who do not have NPD. Evil seems to grow anywhere people, for whatever reason, refuse to examine their motives, actions, and thought against a backdrop of Truth.
I know some Liberals who are on the path to evil only because they consider truth relative and, as such, deem any evaluation of themselves against standards of "truth" unnecessary. They not necessarily narcissistic but might consider sexual freedom or cheating on an exam or shoplifting OK ...and this is the beginning of evil.
I think people who are involved in witchcraft and sorcery are opening themselves up to evil...but whether they have NPD is unrelated to that activity.
Also, his chapter on demonic possession ("Danger--High Voltage) was unrelated to NPD.
My experience is that evil depends on how a person reacts to the inevitable injury that life inflicts of the human spirit.
Some people grow in character, some people simply become angry and diminish in spirit.