Bellatrix Lestrange (also known as Bella by Lord Voldemort and Narcissa Malfoy) is a member of the Black family and a follower of Lord Voldemort in the Harry Potter series. She first appeared in Harry Potter and the Goblet of Fire and the following three books. She appeared in the movies based on the books, with her final appearance being in Harry Potter and the Deathly Hallows - Part 1. She was mentioned in the book Harry Potter and the Cursed Child.
Amongst her actions that led to her imprisonment was kidnapping Alice and Frank Longbottom and using the Cruciatus Curse to attempt to extract information about Voldemort's location, aided in the kidnapping by her husband Rodolphus and brother-in-law Rabastan. The interrogation drove the Longbottoms into insanity, and they spent the rest of their lives at St Mungo's Hospital for Magical Maladies and Injuries, unaware that Alice had given birth to a son less than a year prior to the kidnapping.
As a pure-blood witch, she was related to many influential families in the wizarding community, such as the Malfoys through her sister Narcissa. During the Battle in the Department of Mysteries, she taunted Neville Longbottom, asking him how his parents were, and later tortured him and threatened to do the same to Ginny Weasley. Also during that battle, she was at first amused that Harry Potter would try to bargain in order to keep his Prophecy, but was also incensed that he would dare speak her master's name. Later, after the members of the Order of the Phoenix arrived to rescue Harry and his friends, she began duelling with her niece Nymphadora Tonks and then with her cousin, Sirius Black. She defeated both, with the Curse she used against Sirius knocking him backwards through the Veil that separates the land of the living from the land of the dead.
A year later, she and a group of Death Eaters were able to infiltrate Hogwarts School of Witchcraft and Wizardry with the help of her nephew Draco Malfoy, who had repaired a Vanishing Cabinet. Together, they confronted Headmaster Albus Dumbledore in the Astronomy Tower, to ensure Draco could carry out the task Voldemort had given him, which was to kill Dumbledore. However, Severus Snape intervened and cast the Killing Curse himself, which had previously been arranged between him and Dumbledore as a means to lead to Voldemort's downfall.
Harry, who had witnessed the murder after Dumbledoor's command to remain hidden and do nothing, followed the group as they departed Hogwart's and attempted to strike down Snape, but was easily disarmed as Snape was able to counter the spells Harry was using, some of which Snape had created himself. Snape then prevented Bellatrix from killing Harry, saying, "He is for the Dark Lord."
The following year as Lord Voldemort continued his second rise to power, she participated in an attack on The Burrow, the Weasley's home where Harry Potter was spending Christmas. Her sing-song taunts of "I killed Sirius Black! I killed Sirius Black! You going to get me? You going to get me? You going to get me?" were intended to goad him into following her and separate him from his friends, Ronald Weasley and Hermione Granger. It nearly succeeded, but he was rescued. It should be noted that this event was a scene added to the film Harry Potter and the Half-Blood Prince and is not present in the book.
Later, after Voldemort completed his takeover of the Ministry of Magic, Harry, Ronald and Hermione began their search for Voldemort's Horcruxes, but were captured and brought to Malfoy Manor. Bellatrix held Harry at wand point so that Draco could attempt to make a positive identification before Voldemort was summoned, as Harry's face had been disfigured by Hermione with a Stinging Curse just before they were captured.
Amongst the items the Snatchers discovered was a sword. Angered and frightened, Bellatrix attacked the Snatchers, killing several and demanding to know how those three had come to have it in their possession. Harry and Ronald are put in the dungeon, while Bellatrix began torturing Hermione for the information. At some point during the interrogation, she carved the word "mudblood" into Hermione's arm. The three and two other captives were later able to escape, assisted by Dobby, an Elf, but during the escape, Bellatrix threw a dagger at the group. The dagger followed them through the Apparation passage and struck Dobby, resulting in his death shortly thereafter.
Bellatrix was killed in a fight with Molly Weasley during the Battle of Hogwarts. Initially, she thought Molly no match for her skills, but as the fight went on, she was forced on the defensive as Molly's anger at her children having been attacked gave her the upper hand. A spell cast by Molly caught Bellatrix by surprise at its strength, and her body appeared to draw in on itself, as if it was being desiccated from the inside. Molly's final spell delivered the killing blow, obliterating Bellatrix.