Why doesn't the sword keep grues away? It should glow whenever a grue is near.
Good point. In Spellbreaker, it's said that even light that's very dim by human standards is painful for a grue to look at. On the other hand, some aspects of grues and their fear of light vary Depending on the Writer.
Why couldn't you make friends with the thief? He's a cool guy!
Well, you sorta could. It's very unlikely he'll attack you unless you enter his hideout or try to take his bag. You can even give him treasures if you want.
Remember, the thief steals the torch, i.e. the only light source in the game that doesn't eventually burn out. That's not cool, that's trying to get you killed by a grue.
Every dark area is likely to be filled with grues. Does that mean that residents of the Underground Empire are forced to always have lights on, lest they get eaten by grues?
Yes, In Return to Zork you can actually pay money to rent a room in the inn and if you don't bring your own light source you *will* be eaten by a grue when you turn out the lights to go to sleep.