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Lethally venomous tooth from the dead Basilisk in the Chamber of Secrets -- one of the few substances that can destroy a Horcrux. Harry used one on the diary. Hermione used one on the Cup.
The Basilisk has been dead for five years but its venom remains potent. Ron and Hermione returned to the Chamber of Secrets during the Battle to collect fangs -- the only Horcrux-destroying substance available now that Griphook had taken the Sword. Hermione destroyed Hufflepuff's Cup with a fang in the Chamber. The snake that Salazar Slytherin bred to purge Muggle-borns from Hogwarts provided the weapon that helped destroy Voldemort's immortality. The irony is poetic.
Long, curved, razor-sharp ivory fang. Basilisk venom is one of the most destructive substances in existence -- it dissolves almost anything and has no antidote except phoenix tears.
Also known as: Basilisk fang, Basilisk fangs, basilisk venom