It seems you have an error with Ring of Maiming and Visor of Maiming. We got both items from the same run, so they can't both be the wall chest. Proof: http://i.imgur.com/FE06mP3.jpg
After looking through 5 pages of youtube videos, I finally found one where one of these items is shown to drop: http://www.youtube.com/watch?v=J95V2ive5EA
Visor of Maiming dropped for them from the wall, so Ring of Maiming must be from center.