How would you describe your relationship with this person?

My mom married her second husband when I was 6years old and they were together for 13 years, also a narcissist. I considered him my step dad at the time because that's what my mom called him. Since they divorced he's considered my mom's ex husband. I never felt in my heart of hearts that he was really a father figure to me and he's such a POS that now as an adult I would never refer to him as my step father.

If you feel like he was a step father to you then I think that's a fair title but otherwise I would just say mom's second husband

This was me except they didnt split until I was in my 20s but if cut him off before then other than for handovers of my younger brother if he stayed at mine for the night while my mum was away. I dont refer to him as anything other than "dickhead" or my brothers dad 😂 unfortunately he is still alive.

I’m so sorry you seem like like you have been through a lot