A Death Eater is the name Voldemort's supporters gave themselves during the first Wizarding War. They wear masks to conceal their identity, and hooded cloaks.
Many of the Death Eaters are taken to Azkaban, the wizarding prison, after the first Wizarding War, but some remain free. It appears to be those remaining Death Eaters who cause the trouble at the campsite after the Quidditch World Cup final. They flee when they see the Dark Mark in the sky, Disapparating before any of the Ministry wizards can get near enough to unmask them. Bill Weasley suggests that the remaining Death Eaters would probably be more frightened than most to see Voldemort return. They denied they had ever been involved with Voldemort after he lost his powers, and he is likely angry with them for their desertion.
Sirius Black reveals that there was a group of Slytherins when he was at Hogwarts who nearly all turned out to be Death Eaters. Amongst the group were Rosier and Wilkes, who were killed by Aurors the year before Voldemort fell; the Lestranges, a married couple who are currently in Azkaban and Avery, who wormed his way out of trouble by saying he had acted under the Imperius Curse.
The Death Eaters stand in a circle as Harry is freed from his bonds and handed back his wand. When Harry walks toward Lord Voldemort, the Death Eaters close ranks, forming a tighter circle around the pair and filling in the gaps where the missing Death Eaters should stand. They laugh as Voldemort taunts Harry, mocking his duelling skills, more so when Voldemort forces Harry to bow to him. They do not laugh when Harry resists the Imperius Curse performed by Voldemort, and enjoy watching him attempt to avoid Voldemort's spells. When the golden thread appears, connecting Harry and Voldemort's wands, the Death Eaters shout to their master for instructions, and are told to do nothing. They watch as the effects of the two wands connecting takes place, running in vain after Harry when the spell is broken, but are unable to prevent him from leaving.
Severus Snape reveals that every Death Eater has the sign of the Dark Mark burnt into their forearm by the Dark Lord, as a means of distinguishing each other, and as a way for him to summon them to him. When Voldemort touches the Mark of any Death Eater, the rest were to Disapparate, and Apparate instantly at his side. The Mark burns and turns black when Voldemort summons his followers.
Several Death Eaters arrive in the Department of Mysteries to retrieve the prophecy from Harry and the other students, resulting in a fierce fight between the wizards.
