- “Of the many fearsome beasts that roam our land, none is more deadly than the Basilisk. Capable of living for hundreds of years, instant death awaits any who meet this giant serpent's eye. Spiders flee before it.”
- ―Harry Potter reading from the library book page Hermione held on to
- “Parseltongue won't save you now, Potter. It only obeys me!”
- ―Tom Riddle telling Harry that his ability to speak Parseltongue won't do him any good because he has no control over the Basilisk
The Basilisk is the central main antagonist of Harry Potter and the Chamber of Secrets. She is a fearsome creature with extremely dangerous powers, particularly the ability to instantly kill people who make direct eye contact with her and her venomous fangs, that can only be controlled by Parselmouths like Herpo the Foul, who first created the monstrous snake.
When Hogwarts was founded a 1000 years ago by Godric Gryffindor, Helga Hufflepuff, Rowena Ravenclaw, and Salazar Slytherin, the four eventually had a disagreement as Slytherin believed only all-magic families should be allowed to learn about magic. He left the school as a result; before leaving, he constructed the Chamber of Secrets and hid a female Basilisk that could only be controlled by his Heir inside the Chamber to eradicate all muggle-born students from Hogwarts.
During his time at Hogwarts, Tom Riddle discovered he was a descendant of Slytherin, and found the Chamber of Secrets, unleashing the Basilisk, killing one student, a girl named Myrtle Warren, who was hiding in the second floor girls' bathroom, which had a secret entrance to the Chamber of Secrets under the sink. To ensure Hogwarts wouldn't shut down, Tom framed Rubeus Hagrid for the murder. Albus Dumbledore then kept a close eye on him afterwards. Knowing it was risky to open the Chamber again while still at school, Riddle left a diary containing his 16-year-old self in its pages behind so he could finish what he started in the future.
The Basilisk is a gigantic serpent with greenish-grey scaly skin, flat spikes on the back of the head and along her body (if she were a male, there would be a scarlet plume on her head), sharp fangs that contain potent venom and yellow eyes that can instantly kill people who look directly into them, until Fawkes blinded the Basilisk.
Being a magical creature, the Basilisk is considerably powerful and dangerous. Her venom is potent enough to kill a person in just a little more than a minute. Of course, her huge yellow eyes are what makes her extremely dangerous; anyone who looks directly into them will die instantly. In fact, the Basilisk's gaze is even fatal to the Basilisk herself; if a person were to hold up a mirror in front of the Basilisk and she stares at it, then she would go down as quick as a finger snap.
Harry Potter and the Chamber of Secrets
When Harry Potter starts his second year at Hogwarts, despite warnings from Dobby the house elf, Lucius Malfoy, Draco Malfoy's father, slips Tom Riddle's diary into Ginny Weasley's belongings, resulting in Ginny being corrupted by Riddle's spirit. Under Riddle's influence, Ginny reopens the Chamber of Secrets and unleashes the Basilisk again.
Fortunately, no one is killed, just petrified. Among the Basilisk's victims this time are Mrs. Norris, Colin Creevey (a camera-wielding first year), Justin Finch-Fletchey, and Hermione Granger (who just discovered the Basilisk was the evil creature living in the Chamber thanks to a library book page on her, which she held on to). Harry and Ron find the page when they visit Hermione again in the hospital wing. After learning that the Basilisk had taken Ginny into the Chamber of Secrets, Harry and Ron attempt to save her, with the help of a reluctant Gilderoy Lockhart, who attempts to perform a memory charm on them, but accidentally erases his own memory when it backfires, and causes a cave-in.
Harry is forced to go alone. He finds Ginny as well as Tom Riddle, who tells Harry that Ginny (under his influence) was responsible for all the terrible things that have happened, and then reveals himself to be Voldemort. When Harry expresses support for Dumbledore, Fawkes, Dumbledore's pet phoenix, flies in with the Sorting Hat. Riddle then unleashes the Basilisk to kill Harry. Harry makes a run for the door, but trips on the slippery floor. Fortunately, Fawkes blinds the Basilisk, allowing Harry to face her head-on. Harry manages to get the Basilisk off his trail, but ishe reappears out of the water surrounding the statue of Salazar Slytherin. It is then that the Sorting Hat produces the Sword of Godric Gryffindor. Harry takes the sword and climbs the Slytherin statue; the Basilisk blindly follows Harry's movements. A tense battle ensues, with Harry attacking the Basilisk with wild sword swings, and the monster lunging at Harry, missing and causing minor damage to the statue. The two eventually take their fight to the top of the statue's head. For a moment, it appears Harry has the upper hand, but the Basilisk knocks him down, causing him to almost lose the sword; he retrieves it at the last second and fatally impales the Basilisk through the roof of her mouth as she comes in for the kill. However, as Harry pulls the sword out, one of the Basilisk's fangs falls into his arm, poisoning him.
Harry then uses this fang to stab Tom Riddle's diary, destroying Riddle and saving Ginny from death. Fawkes then heals Harry's injury with his tears and flies them out of the Chamber.
Harry Potter and the Deathly Hallows: Part 2
In Deathly Hallows: Part 2, when Ron and Hermione go down to the Chamber of Secrets to get some Basilisk fangs, the Basilisk's body has decomposed, leaving only her skeletal remains. After they destroy Helga Hufflepuff's cup, one of Voldemort's horcruxes, the Basilisk's skeleton is presumably destroyed.
- Of the three creatures that Harry faces in the series, the Basilisk, the Mountain Troll, and the Hungarian Horntail, the Basilisk is the only one that is a main antagonist.