Have you notice if you walk in the cave after not being in there for awhile there is no rat and if you talk to the hooded guy he gives you a different message then theres like a poof effect and the rat appears? I'm pretty sure it reads: Its dangerous to go alone. or something like that. I have found he will buy the green rupee loot to for 75 gralats and says something like: That gem reminds me of home. and says something else I haven't quite figured out yet when you decline to sell him the rupee.