While not a narcissist, MDMA helped me with some things even if I used with other intentions in mind and it bringed some other stuff that I had to deal later with.
Just an anecdote that seems interesting. I knew a girl that every time she took MDMA in a party setting freaked out because she started to notice, the first time in months, all the selfish shit she had been doing till that point. And I mean stealing from her current boyfriend, lying to her parents so they gave her more money to buy things she didn't need (while being themselves pretty tight on money) and more.
She was diagnosed with really intense ADHD and CPTSD and I suspect she may have autistic traits and maybe narcissism as well, masked by all the other things, but I'm not a doctor.