A Narcissist has no Ego, contrary to what many think. They can't test reality, they are always in "flight or fight" mode ( survival mode). They "use" others to validate their lack of self worth. Others are extensions of them. We don't exist as an outside person, to them. If you stop to give thempositive kr negative reaction, hence validate them, they have to find someone that will or else they decompensate. in extreme cases they feel what is called mortification.  Deep wound.
If you kill ego, you loose the hability to test reality and defend yourself from danger.