I assume by now most of us have played through the storyline at least once but just in case you haven't Gentle Reader, the "spoiler" tag is your warning.
So last night I finished Act III and was treated to Diablo rumbling something to the effect of "Well done, thou good and faithful servant" to Adria moments before shooing her through a fugly portal and possessing his, um, daughter.
My question is this: where's Adria gone? I think we can agree that every time that woman disappears, there's going to be trouble. My own theory can be summed up in one word: EXPANSION.
After you kill Magda you get her diary thingy. In it she says that her and another witch took over the coven from their previous rulers, but then the other witch 'went away' or something like that, while she stayed behind to command them. Pretty sure that 'other witch' is Adria, so we're likely to see more of the coven?