I talked to Minthara and arranged for her to raid the grove, planning to betray her. But when I got to the grove after setting up a massive trap, the raid wouldn't start. I hadn't told Zevlor that I had taken care of Kagha so I had to do that first. I tried talking to him again but the raid still didn't happen. I left the grove and come back, still didn't work. I rebooted the game and still nothing. I ended up reloading a save, loosing several hours of progress.