Holy crap. Saw this last night.
A goblin tower right next to an open chasm. There were chasm creatures everywhere making regular attacks on the tower. I had to turn off the combat announcement screen because the goblin macelord and axelord were taking down dozens of creatures. When I reached the entrance, it was completely covered with blood, ichor and bodies of ratmen, giant moles and goblin drunks.
Entering the tower showed more of the same. Some rooms were clean, but others were just as much of messes as the first room. There seemed to be more creatures than goblins in there. Every time I did come across a goblin, they were being swarmed by invaders.
Finally, after an entire level with no messes(I assumed that all the goblins all traveled down to meet the invaders), I came across the largest one of all. A LOT more bodies, and the occasional guard corpse. In fact, there was nothing left alive. After deciding to enter the roof, I was greeted by the familiar message of a Macelord.
Oddly enough, throwing at good-quality spear at him did a one-hit kill. So deciding that it was just too cheap, I decided the axelord would meet an honorable fate. I met him on the roof.
It was amazing! Batmen flying down on top of us, me slamming antmen into the fortifications with my hammer, explosions of gore everywhere. It was awesome. And the fight itself was something grand. My adventurer died when his head was chopped off, but the axelord died from the batmen because of the injuries I had given him.
I later discovered many immigration waves just outside of the tower. Do massacres cause residents to move away?