there's also an island on the upper left of the map where a lot of grey gnolls spawn, if you wipe them you'll get the others you need for the quest to spawn on the tree bridges. They'll spawn in groups of 2. I had tried going into BB to do this, but that didn't work very well. I was able to solo this at 18, you'll want to make sure you use an HO with gnoll masters strike if you have it almost immediately to take out one of the gnolls in the duo as they heal each other. I was able to have that completed in a little over 25 minutes. Also, when you get to the battle inside the mage tower, make sure you take out the smaller elementals first. the giant one on the first floor is level 47 when you start, but by the time you've taken out the 3 others he'll be down to 19.