This quest is not available in game.
Retrieve the Moldy Tome and Tattered Manuscript for Jorah Annison in the Undercity.
Ah! I see that you are a warlock of similar tastes to mine. Indeed, acquiring the Tome of the Cabal is a worthy aspiration. Did you know that it was once held within the walls of Lordaeron? It was vandalized though, almost half its pages removed. Who would commit such a heinous act?
That half is lost, though rumor says that it fell into the hands of the centaur of the Thousand Needles.
The rest of the text was to be transferred to Ironforge, but was lost in transit on the coast west of Southshore.