Fenrir Greyback

"Delicious girl...what a treat...I do enjoy the softness of the skin..."

- Fenrir Greyback to Hermione

 Fenrir Greyback , a werewolf allied with the Death Eaters, is known for his savagery, and preference for attacking children.

History
Not much is known about Fenrir Greyback's back history. It was unknown who bit him and made him a werewolf.Albus Dumbledore knew of him. He bit Remus Lupin when in werewolf form when Lupin was just a boy, transforming him into a werewolf.

Physical Description
Fenrir Greyback has graying hair and a shaggy appearance, his face covered in matted hair and whiskers. He has pointed brown teeth as well as sores on the corners of his mouth. In his werewolf form, he is covered in gray fur.

Personal Tastes
Fenrir seems to enjoy the taste of humans, even while in human form, perhaps even to the point of cannibalism. If this isn't the case, he at least portrays himself this way in order to intimidate others.

Methods
Greyback is vicious, purposely placing himself near his victims near a full moon, to ensure an attack. He prefers to attack children. "Bite them young, he says, and teach them to hate wizards" (Half-Blood Prince 334 [HC ed.]).

Allegiance with Lord Voldemort
At some point in his life, Fenrir joined Lord Voldemort and the Death Eaters. Because he is not a full-fledged Death Eater, he hasn't been branded with the Dark Mark. This is both an insult to him and a sign that Voldemort's new society has no place for him. Greyback was the leader of the werewolves who were on Lord Voldemort's side, fighting along with them during Voldemort's two attacks on Hogwarts.

As a weapon of the Dark Lord, Voldemort would often use Greyback as a threat to intimidate opponents to do his bidding, sometimes threatening to send the werewolf to attack their children. Draco Malfoy once also threatened to send Greyback to punish Mr. Borgin.

Battle of the Lightning Struck Tower
Fenrir Greyback was present at the Battle of the Lightning Struck Tower, where, though in human form, he viciously brutalized Bill Weasley, biting him and scarring him so badly that Molly Weasley assumed French witch Fleur Delacour would no longer want to marry him, which didn't prove to be the case. Fortunately, as he was in human form, Bill did not become a full-fledged werewolf.

Greyback also tried to bite Harry Potter during the battle, but was thwarted by the Full Body-Bind Curse cast on him, perhaps by Neville Longbottom.

Capture of Harry Potter
Months after this vicious attack on Bill Weasley, Fenrir Greyback and his gang captured Harry Potter, Hermione Granger, and Ron Weasley after they triggered the taboo on Voldemort's name. After working through and nearly falling for the lies the three companions gave, Greyback and his gang brought the three to the Malfoy Manor, where Lucius Malfoy, Bellatrix Lestrange, Draco Malfoy, and Narcissa Malfoy were residing. Greyback hoped to receive the ten-thousand-galleon reward for capturing Potter, and was also eager to bite Hermione. However, the capture was thwarted with the help of Dobby, the Malfoy's old house-elf, and the three escaped with other prisoners of the Malfoys. While Bellatrix Lestrange and the Malfoys were punished by the Dark Lord, who was summoned to the scene but arrived too late, it is unknown if Greyback and his gang were punished.

The Battle of Hogwarts
Fenrir Greyback was present at the Battle of Hogwarts, where he was attacked while attempting to attack Lavender Brown. While he apparently was felled during the skirmish, he was seen later seen as a grey blur running four-legged through the battle (presumably in his human form since Lupin did not change shapes during the battle). During the battle, he was injured by a crystal ball dropped from a higher floor at Hogwarts by Sybill Trelawney. In the end, he may have been defeated by Ron Weasley and Neville Longbottom.

It is unknown if he survived the fight or not.

Name etymology
Fenrir is one of many permutations of Fenrisulfr, the great wolf from Norse mythology. Like Fenrir, he is a savage beast concerned only with hunting and killing.

Greyback is likely simply a reference to his graying hair and gray fur when in werewolf form.

Probable Sources
Greyback is most likely based on French loup-garou tales coming from the 15th to 17th centuries. His language and appearance bear close connections to Jean Grenier. The latter was a young boy accused of being a werewolf. Grenier supposedly claimed that he would eat anything while in his wolf shape but preferred the flesh of young girls. Charlotte Otten relates this story in A Lycanthropy Reader: Werewolves in Western Culture as do Sabine Baring-Gould in The Book of Werewolves and Montague Summers in The Werewolf in Lore and Legend.