It is my second playthrough, and this time I decided to side with the goblins (which was very easy since I played a Drow). After talking with the drow lady I went to the druid grove, but they let me in and decided I am still on their side. In order to start the assault I just started killing people in the camp, and it worked, the goblin came and the raid started. but after killing everything in the camp (including every druid inside the grove, all the tieflings, etc) the quest won't continue. It's seems like the game still thinks there are people left alive but I can't find any...