Probably needs to create a separate thread.
I believe that the mp2 are destroyed upon their defeat (for that player), but it should not matter, because there is a great amount of them in the cave.
From what I know they were not created for the purpose of dueling, but it would help newbies to have someone to fight with. In case this would become their official function, it might be a good idea to mention the opportunity to train with them on one of the boards, probably the one in the cave.
Off-topic: (By the way, I remember there was a npc on mainland some time ago, and it had multiple stages to it, some sort of battle master .. ? Wonder what happened to it. But again, that is another topic ..)