Nymphadora Tonks

Nymphadora Tonks is a fictional character in J. K. Rowling's Harry Potter novels, first appearing in Harry Potter and the Order of the Phoenix (2003). She is an Auror[?] who is especially gifted in the art of disguise. She prefers to be addressed as Tonks and despises her first name. She is especially friendly with Harry Potter, Hermione Granger, and Ginny Weasley. She enjoys conjuring up unusual disguises in the Muggle world though her other skills as an Auror aren't as exceptional. Tonks is also a little clumsy. Tonks is usually accompanied by Alastor Moody.

Wikipedia contains spoilers

During the final scenes of Harry Potter and the Order of the Phoenix, Tonks accompanies Alastor Moody, Sirius Black, Remus Lupin, and Kingsley in fighting the Death Eaters though she becomes injured in the process and falls unconscious. Moody tries to revive her but she remains unconscious and is taken to St. Mungo's Hospital after the fight with Lord Voldemort.