The character does not make another appearance until Harry Potter and the Order of the Phoenix, in which he is appointed by the headmaster, Albus Dumbledore, to teach Divination at Hogwarts in place of Sybill Trelawney, who had been sacked by the High Inquisitor, Dolores Umbridge. When Harry sees Firenze in class, it is obvious that Firenze has been attacked, and it emerges that he was indeed cast out of the centaur herd for agreeing to answer Dumbledore's request for help. Firenze ignored the centaurs' taboo on assisting humans because he felt he had an obligation to contribute to the struggle against Voldemort. At the end of the fifth book, Firenze remained a member of the teaching staff, and in Harry Potter and the Half-Blood Prince he shares teaching duties with a reinstated Trelawney, a situation which she finds distasteful. Dumbledore keeps him on because Firenze would have no place left to go, as he is an exile from his herd.
In Harry Potter and the Deathly Hallows, he is seen near the end of the book fighting alongside the other professors of Hogwarts, helping to defend the school against Voldemort and his Death Eaters; it was mentioned that he was wounded on his flanks by the Death Eaters but ultimately survived the battle. Although not mentioned in the series, according to a J. K. Rowling web chat Firenze's herd is later forced to acknowledge that Firenze's pro-human leanings are not shameful and allows him back into the fold