Who is Narcissa Malfoy from Harry Potter and the Deathly Hallows and what is their importance?

Narcissa Malfoy is Lucious' wife. She and her husband are faithful followers of Voldemort, but she is very displeased with him at this time. At one point, Voldemort sends Narcissa to see if Voldemort has killed Harry. When Harry tells that Draco is alive, she lies for Harry and tells Voldemort that he is dead.