This is a fascinating subject, especially when you get into thinking about how the defense mechanism works (narcissism is the ultimate defensive mechanism, which is why there is no known cure) and how it fuels the narcs interactions with people. I will post a link at the end of this if it intrigues you.
Every human has narcissistic characteristics, at a moderate level it is very healthy. We all must have some form of self confidence and ego to get through life after all.
It is possible to have a very narcissitic, competitive and selfish personality but to still actually care about people close to you. The overly narcissitic would come across as somewhat arrogant jerks, that loved themselves a little too much and whom could be somewhat manipulative. They can sometimes take criticism though and might not mind admitting their narcissitic qualities, perhaps even admitting to being a bit of a jerk.
And then we have people whose ego is so troubled that they have the full on personality disorder. This can range from a mild case to an extreme case.. antisocial personality disorder is arguably nothing but an extreme version of npd. Some think sociopathy is due to a different brain structure, but there is no proof, people argue this ad infinitum, so clearly.. there is no proof. I will certianly not be so arrogant as to concretely say my opinion is correct (which every damn nt ALWAYS DOES) Anyway for the intention of defending onself it's probably easier to see npd and apd as two ends of the same spectrum.
I digress.. The personality disorder is thought to be quite a different beast from the merely overly narcissistic people. It is thought to be casued by childhood trauma, where the child is devaluated or unloved by their parents. In our youths it is normal to fantasise and have fun imagionary worlds to escape to, often in these worlds we see ourselves as superpowered versions of ourselves It is a child's healthy reaction to being born in an insanely complicated world that they can not yet make sense of. (none of us ever can completely). Sometimes they retreat to some little pocket of their imagination where they can have more control over reality. Due to emotional abuse the narcissist will never grow out of this fantasy phase and to protect their young minds from pain they will always have a grandiose version of themselves that they believe to be the real them, all the while the true, original innocent personality is stuck inside an armoured shell.. sometimes the original personailty can be seen in rare circumstances, but not at the sociopathic end, I would refer to this person as a corpse in shining armour.
How does the grown up fantasist continue to see themselves as this godly version of themselves, surely adults in the real world will bring them back down to earth?
Unfortunately narcissism is the ultimate defense mechanism..they will go through life doing everything in their power to manipulate your opinion of them, they will will wear a mask, a differnt mask for diferent people, whatever is most efficient at extracting attention and praise from whoever they're talking to, whatever is most efficent at making you believe that their fake self is real.
We all have some kind of feedback when we are talking to people, we may say something that the other person doesn't like and we will see in their face that they are perhaps offended or disgusted with us, most of us want people to think well of us, so a normal person may try to correct this by placating the other person, perhaps even lie, and say they meant something in a differnt context, perhaps being a little fake , then again we may not even care. Not so with the narcissist.. the narcissist takes this to an extreme level, they cannot bare for any response except awe, admiration, praise, or perhaps fear, becasue fear would still signify that they are powerful. So they go through life wearing these masks, they learn from every single minute interaction on how to become a more skilled manipulator. Even a narc with half of somebody's intelligence could still manipulate an average person a reasonable amount of the time (theyd probably be a one trick pony though). Aspies.. think about how well you can recall every detail of your obsessive interests. The narc also has this ability to HYPERFOCUS on controlling people, because they need to, in order to keep their false self "alive" If for a second they realised they are basically a fake persoanlity they would repress it in, and withdraw in horror. They are the ultimate fake. You may think you are talkign to a real personality.. but it just doesn't exist. This has bizzare philisophical implications
As to the evil part, I can't be assed to write anymore, read it from someone older, wiser, and more eloquent than me. http://www.escapeabuse.com/npd.pdf
Oh, some narcissists live off the fear a lot more, and surround themselves with people who admire badasses, so consequently they don't mind negative attention. And can admit they are evil.. it is probably only the higher level sociopath that is capable of this.
Also, if the narc has other disorders as well, they might get in the way of the main defense mechanism, meaning that the original personality may break through the armour more often.
This is deeply distressing, and my empathy hits overdrive when I realise what is happening... however there is still a possibility that I was just manipulated and they were faking this to draw me back in.