Narcissists seek attention, plain and simple.  They thrive off of baiting others into conflict and needless interactions.  The same generally goes for Borderlines and other various disordered exes.

When baiting is an issue (i.e. the narcissist acts out in one of their many attention-seeking ways), the best antidote is to remain deeply focused on your own vision of what you are working to create in your life.  The narcissist seeks to divert your attention away from you own life so they can have your attention for themselves.  Don't give it to them.