Okay, the centaurs... here's some of it anyway. I've just included the dialogue....
Bane - What are you doing? You have a human on your back! Have you no shame? Are you a common mule?
Firenze - Do you realise who this is? This is the Potter boy. The quicker he leaves the forest the better.
Bane (angrily) - What have you been telling him? Remember Firenze, we are sworn not to set ourselves against the heavens. Have we not read what is to come in the movements of the planets?
Ronan - I'm sure Firenze thought he was acting for the best.
Bane - For the best! What is that to do with us? Centaurs are concerned with what has been foretold! It is not our business to run around like donkeys after stray humans in our forest!
Firenze - Do you not see that unicorn? Do you not understand why it was killed? Or have the planets not let you in on that secret? I set myself against what is lurking in this forest, Bane, yes, with humans alongside me if I must.
This passage has always confused me. Are the centaurs predicting that Harry will do something terrible, or is it the case that he has such an important path to fulfil that the centaurs are afraid to change his path, even in the slightest turn? In some ways the centaurs remind me of the ents from LotR. They both have the power and possibly the disposition to do good, but they choose to be inactive in the events of the world, even to the detriment of what is good and right. The ents ignore and wish to be ignored, the centaurs like to predict and observe.
What I would like to know? What path do the Centaurs see ahead for Harry? And like the ents, will they eventually be forced to act against evil? Perhaps Voldemort will cloud the stars like Saruman clouds the sun, finally rallying the centaurs....