I never determined how to open a lock outside a room with a chute that when you entered the narrator said wasn't big enough for people. I also don't know what to do with the chute.

Can you open the gate by the back door? (leads to the naga)

Thanks in advance. Finished the rest.

I believe the lock you're referring to leads to Kol the Heretic's secret room. Use the Heretic key on the lock. Inside you will find a statue of Kerath and some goodies. As for the chute, you can peer down it, but other than that, it doesn't serve much purpose, I don't think. If you're having a problem with dead monkeys, I suppose you could stuff a few down the chute to get rid of them.

Serath

The naga gate by the back door doesn't open. You get to the naga by opening a secret door in the big statue in the big room with brazier.