Ex Libris was an old, hidden archive underneath New Cavendish Library, visited often by Yvonne Hartman to gain intelligence regarding alien activities or species. The archive was run by Mehdi.
In late 2005, Hartman met with Mehdi to discuss Planet XXX and its dominant species. When she unexpectedly came under attack from Kieran Frost, she had to take the paperwork and flee. (AUDIO: Through the Ruins)