Narcissists constantly pick fights, debates and arguments. There are so many reasons to why a narcissist frequently argues but to name a few reasons off hand-
to feed their self-hate via initiating negative feedback(all done on a conscious level)
to rid the guilt they hold regarding something they have done
to mentally drain their victim
to cause confusion
to protect their fragile ego which interprets almost everything as an insult
to get out of plans
to escape accountability
to achieve supply.
This is by far an exhaustive list and one would only think the narcissist would not want to exhaust himself by doing such. The reason why the victim of the narcissist is so mentally drained though is that the narcissist has in fact reaped all of their energy thus, the narcissist ever being exhausted. This is a very strange way to live I must say but nonetheless, this is how the narcissist operates. The victim of any narcissist engages in frequent introspection due to constantly needing to reflect on what, how, and why they said what they said to the narcissist to cause such an argumentative and nonsensical, reaction which also exhausts and depletes the victim of their energy.