Bellatrix Lestrange

In this book, Rowling used Albus Dumbledore's Pensieve as a plot device to reveal that Bellatrix, rather than deserting her leader like many other Death Eaters, was part of the group of dark wizards - along with Rodolphus, Rabastan, and Barty Crouch Jr - that tortured well-known Aurors Frank and Alice Longbottom in an attempt to gain information about Voldemort's location.[3] For using the Unforgivable Cruciatus Curse to torture the Longbottoms until they went insane, Bellatrix and her three associates were sentenced to life imprisonment in Azkaban. At her trial, Bellatrix proudly and defiantly proclaimed that "The Dark Lord will rise again, Crouch! Throw us into Azkaban; we will wait! He will rise again and will come for us, he will reward us beyond any of his other supporters! We alone were faithful! We alone tried to find him!"[4] Later in that book, during his rebirthing ritual, Voldemort stated that the Lestranges were amongst the most faithful members of his inner circle.[5]

Fourteen years after Voldemort's fall, Bellatrix was one of the many Death Eaters who escaped Azkaban and rejoined him. After escaping from prison, she was present at the Battle of the Department of Mysteries in the climax of the book, in which a group of Death Eaters attempted to steal Sybill Trelawney's prophecy pertaining to Voldemort's downfall. Rowling let Bellatrix prove her magical prowess during the mission when she overpowered her niece Tonks and Kingsley Shacklebolt in one-on-one duels, killed her cousin Sirius by blasting him through the veil in the Death Chamber, and deflected one of Dumbledore's spells as she made her escape. Harry attempted to use the Cruciatus Curse on her in revenge for killing Sirius, but the curse was ineffective due to the lack of real cruelty behind it ("You need to mean them, Potter! Righteous anger won't hurt me for long.").[6] Before she could do any more, Bellatrix was joined by her master, who ignored her warning that Dumbledore was in the building. Bellatrix was subdued by Dumbledore in the Ministry of Magic's Atrium while he duelled Voldemort. Voldemort interceded on Bellatrix's behalf, grabbing her and taking her with him as he Disapparated, though not before being glimpsed by Ministry officials.

At the beginning of Harry Potter and the Half-Blood Prince, Bellatrix attempts to keep Narcissa from confiding Draco's secret mission to Snape at Spinner's End. Rowling used the conversation between Snape and Bellatrix to imply that Voldemort is still furious at Bellatrix's failure in the previous book.[7] That conversation also suggests that Bellatrix mistrusts Snape not only because of his low birth, but also for many valid questions about his loyalty to the Dark Lord. Snape surprises Bellatrix by replying to each of her arguments and by agreeing to create an Unbreakable Vow with Narcissa to assist Draco in his mission to kill Dumbledore. Later in the book, it is mentioned by Snape that Bellatrix had been teaching Occlumency to Draco, in an effort to aid him with his mission. In the film, she and Fenrir Greyback arrive at the Burrow (the Weasley house) and burn it down. Harry and Ginny chase after them, with Bellatrix taunting "I killed Sirius Black!".

The first chapter of Harry Potter and the Deathly Hallows implies that Voldemort is still angry with Bellatrix, as evidenced when he makes fun of the fact that her niece Tonks married werewolf Remus Lupin.[8] However, Voldemort gives Bellatrix a chance to "prune" her family tree during the Death Eaters' attempt to capture Harry as the boy departs from the Dursleys' home, during which Bellatrix unsuccessfully tries to kill Tonks.[9] In this book, Rowling reveals that Bellatrix is the guardian of Helga Hufflepuff's cup (though she is unaware of its true nature), which Voldemort has entrusted the Lestranges to keep in their Gringotts vault. Bellatrix and the Malfoys detain Harry, Ron, and Hermione at Malfoy Manor, and Hermione is tortured by Bellatrix when she suspects the trio has broken into her vault, but Dobby appears and saves the prisoners, though not before being hit by a knife thrown by Bellatrix as they disapparate to safety. Later in the book, Harry, Ron, and Hermione use a stray hair of Bellatrix's to disguise Hermione as Bellatrix using Polyjuice Potion, in order to gain access to the Lestrange's Gringotts vault. Though Voldemort apparently punishes Bellatrix and the Malfoys severely for interrupting his Elder Wand side quest only to have Potter escape and steal the cup, she nevertheless fights for her master in the Battle of Hogwarts towards the end of the novel. Rowling stated in an interview that, during the battle, it was Bellatrix who killed Tonks. When the battle resumes inside the Great Hall after Harry's supposed death, Bellatrix simultaneously duels with Hermione, Ginny, and Luna, none of whom is a match for Bellatrix, who nearly hits Ginny with a Killing Curse. An enraged Molly Weasley engages Bellatrix in a duel and fires a curse that hits Bellatrix right over the heart, killing her.[10] Rowling revealed that, though there was speculation that Neville would kill Bellatrix, she had always intended Molly to do so because the author wanted to match Bellatrix's obsessive love with Molly's maternal love.[11]

In this play, which takes place over 19 years after The Deathly Hallows, it is revealed that Bellatrix is the mother of the story's antagonist Delphini, whom she had with Lord Voldemort during their stay at Malfoy Manor prior to the Battle of Hogwarts.