i was looking at some close up pictures on az dunno why but I saw a very strange key around his neck I beat the game and never saw him again. does anyone know if he has something to do with those 3 locked power plant doors?
We don't know. Game Freak haven't said anything, and nothing in the game besides the key hints this. Honestly I don't think the key is for the power plant. Remember the Team Flare grunt who was trying to get into the power plant with a pass and not a key? I think the key is for the ultimate weapon that AZ activated, though that is just a theory.