Chamber of Secrets
Hogwarts legend holds that Salazar Slytherin sealed a hidden chamber somewhere in the castle before he left the school, to be opened by his true heir alone, with a monster shut inside it.
A legend told at Hogwarts holds that Salazar Slytherin built a hidden chamber somewhere in the castle before he left the school, and sealed it so that none but his own true heir could ever open it. Slytherin had quarrelled with the other three founders over whether children of Muggle parents should be taught magic at all, and the story says he shut a monster inside the chamber to finish the purge of the school that he could not carry out himself. Headmasters and teachers have searched the castle for it across the centuries and turned up nothing, and most of the staff treat the tale as a story and no more.
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