Oh cool, Dunem, a great blob composed of flame that has a knobby shell and undulates rhythmically has come to set the lower caverns on fire. (Dunem is the red B on the right. The dark grey squares on the bottom right represent smoke. This is way more riveting then I am letting on.)
EDIT: As of 00:06 PST, Dunem has yet to figure out how to cross the underground rivers but it has definitely burn all trees and foliage to a cinder on the eastern banks. I’m kind of pissed about this because I wanted to burn those trees myself so the dwarves could have some fuel. But whatever. Fire blobs, what do you do?