Snakes

Snakes are a type of reptile that hold a profound and often sinister significance within the wizarding world. They are most famously associated with Salazar Slytherin, one of the four founders of Hogwarts School of Witchcraft and Wizardry, and as a result, they serve as the emblem for Slytherin House. This connection extends to the Dark Arts, with many Dark wizards, most notably Lord Voldemort, adopting the snake as a symbol of power and fear. The ability to speak with snakes is a rare magical skill known as Parseltongue, a trait possessed by Salazar Slytherin and his descendants, including Lord Voldemort. Harry Potter's own ability to speak Parseltongue was a source of great confusion and suspicion for him and his peers, as it was widely considered the mark of a Dark wizard.

The snake is one of the most powerful and recurring symbols in the series, primarily representing the legacy of Slytherin and its association with dark magic.

• The Slytherin Connection: The serpent is the official symbol of Slytherin House, representing its founder's most famous ability, Parseltongue. The entrance to the Slytherin common room requires a password, and the entrance to the Chamber of Secrets could only be opened by speaking Parseltongue to a carving of a snake. This enduring link has contributed to the house's often undeserved dark reputation.
• The Dark Arts and Lord Voldemort: As the Heir of Slytherin, Lord Voldemort fully embraced this serpentine symbolism. His terrifying calling card, the Dark Mark, depicts a skull with a snake emerging from its mouth. He also kept a giant snake, Nagini, as a constant companion, a deadly weapon, and ultimately, as one of his Horcruxes.
• Parseltongue: The ability to communicate with snakes is almost exclusively hereditary, passed down through the Slytherin bloodline. Because of this, Parselmouths are viewed with deep distrust in the wider wizarding world. When Harry Potter was revealed to be a Parselmouth, many students suspected he was the Heir of Slytherin. Albus Dumbledore later explained that Harry's ability was not innate but was instead transferred to him from Voldemort on the night his parents were killed.

While ordinary, non-magical snakes exist in the wizarding world just as they do in the Muggle world, some serpentine creatures possess unique magical properties. All snakes, whether magical or not, can communicate with and understand a Parselmouth. Harry's first known use of Parseltongue was with a captive Boa Constrictor that clearly understood his questions about its life and origins. Magical serpentine beasts, such as the Basilisk, are exceptionally dangerous and rare. These creatures often possess deadly abilities far beyond those of normal snakes, such as a fatal gaze or highly potent venom.

• The Basilisk: A gigantic serpent known as the “King of Snakes.” The Basilisk that lived within the Chamber of Secrets was bred by Salazar Slytherin and could only be controlled by his heir. Its gaze was instantly fatal to anyone who looked directly into its eyes, and its venom was so powerful it could destroy Horcruxes. It was slain by Harry Potter in 1993 using the Sword of Gryffindor.
• Nagini: Lord Voldemort's massive, venomous snake. She was fiercely loyal to her master and carried out his orders, including attacking Arthur Weasley and killing Severus Snape. Voldemort turned Nagini into his final Horcrux, making her a vessel for a piece of his soul. She was killed by Neville Longbottom with the Sword of Gryffindor during the Battle of Hogwarts.
• Boa Constrictor: The first snake Harry Potter communicated with. During a visit to the Surrey zoo for Dudley Dursley's birthday, Harry inadvertently caused the glass of its enclosure to vanish, allowing the snake to escape. The snake, which had been bred in captivity, thanked Harry before slithering away, promising to visit Brazil.

• In the film adaptation of Harry Potter and the Philosopher's Stone, the Boa Constrictor from the zoo is changed to a Burmese Python (film).
• The supplementary Fantastic Beasts: The Crimes of Grindelwald film established that Nagini was once a human woman who was a Maledictus—a carrier of a blood curse that would eventually and permanently transform her into a beast (film).
• In a 2007 interview, J.K. Rowling noted that while Harry Potter lost the ability to speak Parseltongue after the fragment of Voldemort's soul inside him was destroyed, he was quite glad to be rid of the “unsettling” ability (J.K. Rowling interview).