From WoWWiki
The Great Ossuary is located inside Scholomance, directly south of the large unnamed central chamber. The upper level is full of plagued dragon whelps and a few necromancers, and contain stairs and numerous chutes leading down into the ossuary proper. An ossuary is a recepticle where bones are buried, and huge piles of bony remains are stacked along the wall on the lower level. This is also where Rattlegore and the Death Knight Darkreaver can be found. The ossuary is a dead-end, but players have to come here to obtain the Viewing Room Key if they wish to progress further into the instance by taking the eastern fork from the main chamber.
