I also learned a bit more about the game's story. Apparently Lloth, the spider goddess worshipped by the drow, has disappeared. Since many drow priestesses draw power and strength from Lloth, the disappearance has caused a power struggle. One drow rebel is able to command an unusual amount of power, and uses it to create an army of drow, mind flayers, and duergar. The motley army attacks Waterdeep and is close to bringing the fabled city down.