There is a letter from the Shadow Druids to Kagha, it takes a perception check to find it. I think it's bugged and doesn't open up new dialogue choices however. My main issue with the fight was that the mephits' summons had bugged AI and would be stuck on "Plotting next move" for several minutes. And yeah, the amount of running water there made it very difficult to use Astarion.
Ah thats the thing all 4 of my partymembers failed to see I guess xD
