Note that for any of this to happen at all, you must have accepted the wand from Mr. Malwick back at Emerald Island at the start of the game.

Further, in answer to the first post in this thread, when the messenger tells you to see Niles Stantley, you have two weeks to get to him. If you do not speak to him within the time limit, the next time you enter the Harmondale map, Harmondale is under attack. I do not know, however, what Niles will say if you try to speak to him after two weeks has passed, but before you return to Harmondale and whether or not you can be attacked and get the tapestry quest in the same game. If anybody knows, please share. What I do know, is that you do not get any reward or exp from bringing Niles the tapestry. There`s exp in killing the guards only.