Pre-1994 Department of Mysteries Visitor

""Bartemius! Not trying to lure Potter into one of the Ministry's summer internships, are we? The last boy who went into the Department of Mysteries never came out!""

- Barty Crouch Jr. (disguised as Alastor Moody) to Barty Crouch Sr.

This wizard (presumably) entered the Department of Mysteries before or during 1994 and never escaped. It is implied that this "boy" died there, probably due to some unknown experimentation. Since Bartemius Crouch, Jr. knows about this occurence, it could have happened as early as the 1970's or even much before. All we know is that he was the "last" one to enter, before Harry Potter, Hermione Granger, Ronald Weasley, Luna Lovegood, Neville Longbottom, and Ginevra Weasley battled there in the summer of 1996.