[thatguy]

I know what you mean.
The other bosses were just put there. Anyone you might have fought in the dark portal A.K.A. "N-Zone," were X-Deaths minions, and I think I know now who you're talking about. If they talked about him in the library then you were talking about Omega or Shinryuu. Omega is that robot looking thing that walks around and is almost impossible to beat without fire rings. Shinryuu is the boss you fight when you open up the chest at the bottom of the stairs, and is impossible to beat if you don't have your characters maxed out.
Although you say its name starts with a p so now i'm curious myself of who you're speaking of, so I'm going to check right now to see exactly which boss it was.

Alright since I can't double post I'm putting what I found on this post. I got a list of bosses that appear in the N-Zone:
Karophysteli
Omega
Apanda
Apocaryopus
Catastrophe
Harkarunassoso
Twin Tania
Shinryuu
Necrophobia
I couldn't find anyone with a p in the beginning of their name but their are quite alot of bosses with p's following up after A so you could have gotten them confused. At this point I would say it's safe to say that you were talking about Nerophobia.
Also if it's not too much to ask, I'm sort of new here, my friend told me about this site, and told me to go to the Noob posts but I didn't, so I don't really know anybody here, it might be helpful having a TFF friend.