Somewhere at the book, Professor Quirrell(who turn to be...) said that Voldemort found the Chamber of secret. Then he ask Harry why did Salazar created the basilisk(instead of just write whatever he wanted), and the answer was the interdict of Merlin. So I guess he learned it from there.
Somewhere at the book, Professor Quirrell(who turn to be...) said that Voldemort found the Chamber of secret. Then he ask Harry why did Salazar created the basilisk(instead of just write whatever he wanted), and the answer was the interdict of Merlin. So I guess he learned it from there.
Mod note: Added spoiler tags