Event on Colossal Cavern

Your scout, Millhaus, reports back, "Sire, there's a brute of a barbarian up ahead. A few dozen ogres, some war trolls, and a few cyclops, I could see. What else there might be, I can't say. There are a couple more ogre villages up there, too. He might be gathering his forces from there. Unless I'm missing something, there's no other way in or out."