The thing I love about this game is there are so many ways to approach a problem. The only limitation is your own imagination. I was going to suggest throwing sleeping potions at the ground, so it splatters on them and makes them fall asleep instead. I wasn't sure if using non-lethal damage would work, because their HP is so low, just the bludgeoning damage might kill them :x I'm glad invisibility worked for you
Zozo is right, there is a part towards the end where there are a TON of them. I just walked passed them without triggering them all, which was nice :x
