Corvinus Gaunt

Corvinus Gaunt was a wizard, and a member of the pure-blood House of Gaunt. As such, he was one of the direct descendants of Salazar Slytherin and was a Parselmouth. Gaunt knew about the Chamber of Secrets, and he was instrumental in keeping the entrance to the Chamber a secret.

In the 1700s, there was a proposal to install an elaborate plumbing system at Hogwarts Castle. This, of course, threatened the secrecy around the entrance to the Chamber of Secrets which, at the time, still had its original appearance - a concealed trapdoor and a series of magical tunnels - and which was located on the site where a girls' bathroom would be set up.

Corvinus Gaunt was, at the time, a student at Hogwarts and, as a descendant of Salazar Slytherin himself, knew where the entrance to the Chamber was and how to open it. Corvinus was responsible for secretly protecting the entrance, having concealed it behind plumbing fixtures and a sink, so that those who knew how could still access the Chamber.