I wrote to Albus, describing, perhaps insensitively, the wonders of my journey, from narrow escapes from chimaeras in Greece to the experiments of the Egyptian alchemists.
Now the fire was mutating, forming a gigantic pack of fiery beasts: Flaming serpents, chimaeras, and dragons rose and fell and rose again, and the detritus of centuries on which they were feeding was thrown up into the air into their fanged mouths, tossed high on clawed feet, before being con-sumed by the inferno.
Goyle was too heavy and Malfoy’s hand, covered in sweat, slid instantly out of Harry’s — "IF WE DIE FOR THEM, I’LL KILL YOU, HARRY!" roared Ron’s voice, and, as a great flaming chimaera bore down upon them, he and Hermione dragged Goyle onto their broom and rose, rolling and pitching, into the air once more as Malfoy clambered up behind Harry.
There are no more uses of "chimera" in the book.
Show samples from other sources
She describes his dream as a political chimera.
Flaming serpents, chimaeras, and dragons rose and fell and rose again
J.K. Rowling -- Harry Potter and the Deathly Hallows