Macnair is a brutal Death Eater. We have met him before: he has been employed by the Ministry for Magic, and he was called upon to execute Buckbeak the hippogriff at the end of Book 3. Macnair is the representative that Voldemort sends to bring Golgomath and the giants over to his side. Hagrid comments, "Macnair, remember him? Bloke they sent ter kill Buckbeak? Maniac, he is. Likes killin' as much as Golgomath; no wonder they were gettin' on so well" (20.150). Macnair is also present at the Department of Mysteries battle, where he tackles Harry bodily and has to be thrown off with the help of Hermione poking him in the eye with her wand.