Slay Squeeg Idolhunter and then report back to Sapper Steelring at Westguard Keep.
So, I hate to say it, pal, but while you were out, the captain took a keener interest in that place.
Looks like he wants my old Explorers' League boss in there dead. My guess would be that we're gearing up for an offensive to clear out the rest of them, and the captain wants their head lopped off, as it were.
Do me a favor? Head back into Whisper Gulch and put an end to Squeeg Idolhunter. From what I remember, my guess would be that he's in the cave in the northwest corner.