Final answer:
Dolores Umbridge heads the Muggle-Born Registration Commission during the Death Eaters' control in the Harry Potter series, targeting Muggle-born witches and wizards.
Step-by-step explanation:
When the Death Eaters take control in the Harry Potter series, Dolores Umbridge is put in charge of the Muggle-Born Registration Commission, not the Department of Magical Law Enforcement, the Department for the Regulation and Control of Magical Creatures, or Werewolf Support Services. This commission was a reprehensible initiative by the Ministry of Magic, under the influence of Voldemort and his Death Eaters, to persecute Muggle-born witches and wizards, presumably to create a 'pure' wizarding race without Muggle interferences.