Nagini

Nagini was the giant, venomous snake who was a constant companion to Lord Voldemort. She was fiercely loyal to her master and served him as a formidable weapon and servant. More significantly, Nagini was also one of Lord Voldemort's seven Horcruxes, containing the final piece of his soul, which made her destruction a critical step in his ultimate defeat. She shared a unique, quasi-telepathic bond with Voldemort, allowing him to possess her and see through her eyes.

Nagini's origins prior to her association with Lord Voldemort are not described in the original seven novels. Her first appearance is in the summer of 1994, at the derelict Riddle House. At this time, she was instrumental in sustaining Lord Voldemort's weak, rudimentary physical form by providing him with her venom, which was milked by Peter Pettigrew and mixed with Unicorn blood. It was during this period that Frank Bryce, the Riddle House's caretaker, overheard Voldemort and Pettigrew's plans and was subsequently murdered by Voldemort, with Nagini as a witness. Shortly thereafter, Lord Voldemort murdered the Ministry of Magic employee Bertha Jorkins and used her death to transform Nagini into his final Horcrux. Albus Dumbledore speculated that Voldemort's deep affinity for snakes and his connection as a Parselmouth made her a fitting, if risky, choice for a living vessel for his soul. Throughout the Second Wizarding War, Nagini played an active role. In December 1995, Voldemort possessed Nagini to attack Arthur Weasley, who was guarding the Department of Mysteries. Harry Potter witnessed the entire attack from Nagini's perspective due to his own Horcrux connection to Voldemort, allowing him to raise the alarm and save Mr. Weasley's life. In December 1997, Nagini was placed inside the corpse of Bathilda Bagshot in Godric's Hollow as a trap for Harry Potter. When Harry and Hermione Granger arrived seeking the Sword of Godric Gryffindor, Nagini, speaking Parseltongue through Bagshot's mouth, lured them into the house. She then revealed herself and launched a vicious attack, nearly capturing Harry for her master before he and Hermione managed to escape. During the Battle of Hogwarts on 2 May 1998, Voldemort was acutely aware of Nagini's importance as his last remaining Horcrux. He magically encased her in a protective sphere to keep her by his side and out of harm's way. However, during a lull in the fighting, he dispatched her to the Shrieking Shack where she fatally attacked Severus Snape on Voldemort's command, as Voldemort wrongly believed this would make him the true master of the Elder Wand. In the final confrontation in the Great Hall, when all seemed lost, Neville Longbottom defied Voldemort and, pulling the Sword of Godric Gryffindor from the Sorting Hat, beheaded Nagini with a single stroke. The destruction of his final Horcrux rendered Voldemort mortal, paving the way for his defeat at the hands of Harry Potter.

Nagini was described as a massive green snake, approximately twelve feet long and as thick as a man's thigh. She was immensely strong and terrifyingly swift. As a creature, Nagini was fiercely loyal and obedient to Lord Voldemort, her creator and master. She displayed considerable intelligence and cunning, as shown by her ability to follow complex instructions and execute the ambush in Godric's Hollow. Her personality was predatory and aggressive, and she attacked her victims without hesitation. Voldemort showed a unique affection for her, often stroking her and speaking to her in Parseltongue, a language she clearly understood. Their bond was exceptionally deep, likely enhanced by the fragment of Voldemort's soul she carried within her.

• Horcrux Nature: As a Horcrux, Nagini contained a piece of Lord Voldemort's soul. This not only tethered him to life but also seemed to grant her an unnaturally long lifespan and a deeper connection to her master than an ordinary animal would possess. Her destruction was essential to making Voldemort mortal.
• Potent Venom: Nagini's venom was extraordinarily toxic and had magical properties that inhibited the healing of wounds. Arthur Weasley's bites required a rare Antidote and a long stay at St. Mungo's Hospital for Magical Maladies and Injuries to counteract its effects.
• Telepathic Link: She shared a powerful bond with Voldemort, allowing him to share her senses, see through her eyes, and direct her actions from afar. This link was so strong that Harry Potter could also access it due to the fragment of Voldemort's soul inside him.
• Physical Combat: Her sheer size, strength, and speed made her a lethal physical threat, capable of constricting and killing a grown man with ease.

• Lord Voldemort: Nagini was Voldemort's most cherished companion and servant. He trusted her above all his Death Eaters, and she was a living symbol of his heritage as the Heir of Salazar Slytherin. He protected her fiercely once he realized his other Horcruxes were in danger.
• Harry Potter: Nagini was a direct instrument of Voldemort's will against Harry. Harry experienced her attack on Arthur Weasley through her eyes and later fought for his life against her in Godric's Hollow.
• Neville Longbottom: As the one who ultimately destroyed her, Neville Longbottom holds a key place in Nagini's story. His act of beheading her with the Sword of Godric Gryffindor was a defining moment of heroism, marking his transformation into a true Gryffindor hero and sealing Voldemort's fate.

The name Nagini is the feminine form of Nāga, a word from Sanskrit for a deity or semi-divine being in the form of a great snake, prominent in Hindu and Buddhist mythology. These beings are often depicted as powerful, intelligent, and sometimes royal, which reflects Nagini's status as Voldemort's revered and formidable companion.

In the Harry Potter films, Nagini is primarily portrayed as a large python, sometimes specifically identified as a reticulated python, though her on-screen appearance varies slightly between films. The film Fantastic Beasts: The Crimes of Grindelwald retroactively established a backstory for Nagini, revealing that she was once a human woman. She was a Maledictus, a carrier of a blood curse that would eventually and irrevocably transform her into a beast. As a human, she was a performer at the Circus Arcanus before escaping with Credence Barebone. (Fantastic Beasts: The Crimes of Grindelwald) J.K. Rowling later clarified that a Maledictus is different from an Animagus, as the transformation is involuntary and permanent, and the curse is passed down from mother to daughter. (J.K. Rowling on Twitter)