Six down, three to go. Our next Black Temple boss guide looks at a lady with more arms than should be strictly comfortable, Mother Shahraz.
Upon killing the last of the previous three bosses, which can be killed in any order -- Teron Gorefiend, the Reliquary of Souls and Gurtogg Bloodboil -- you'll see a message indicating that the door to the Den of Mortal Delights has been opened. This means it's time to pay a visit to Mother, although you don't need to iron your shirt for this particular drop-in.
What you will need, however, is shadow resistance -- and lots of it. The encounter is primarily resistance-based, and requires the epic craftable shadow resistance gear. This in turn requires Hearts of Darkness, which drop from Black Temple (and occasionally Hyjal) trash, so if you've blazed through the instance so far, chances are you won't have enough to kit out your raid group.