The Locked Diary item is one of the biggest mysteries in the new Modern Warfare 3 update to zombies mode. The new season adds extra wonder weapons, schematics, and there's also a new warlord and stronghold coming when the reloaded update arrives. Most importantly, though, there's a new special mode called Dark Aether Rifts and a story mission that leads you to unlocking them.
These function a little like Koschei Complex in DMZ, with a separate timer once you enter via the main MWZ mode. The map will also be pretty familiar to DMZ fans, since it's the Al Bagra Fortress island from Al Mazrah. Everything you have to do in terms of getting the Locked Diary and actually using it is very challenging, so it's inadvisable to attempt this if you've just started zombies.
