Gnolls are more active during the day, according to the locals, and they've encountered a few already, but the Commander must have healed up and gathered a new group of warriors to help him.
If he's rampaging through the spiders, that's Cain's cue to switch tactics and go after him with something more durable. But first, they should go to town and collect some of these quests. A few more levels would do him a world of good in bringing that thing down.
"If you'll all excuse me, higher-level Gnolls are rampaging through my summons outside the valley. I'm going to have to take care of that in person." Cain informs the farmers, hoping that they'll take it as him being conscientious about their safety.
"Should we gather the warriors? We've faced plenty of Gnolls in our time." Dash says, getting to his feet.