Message from the Shadows

I know my brother has been misguided in the past, but I fear that he may have fallen in with an unthinkable evil. He recently began meeting in secret with a dark cult, hidden amongst the people of Dalaran. I travelled here to try to convince him of the error in his ways, but he would not be shaken from his course. Now, he has disappeared. When I last saw him, Raest was staying in a room upstairs. I was unable to find any clues there, but you might fare better.