Tasked to kill a boss in a dungeon which doesn't physically exist - I've checked the dungeon for about 2 hours and pretty much scoured every inch of this place. Either the boss is in another dungeon or he doesn't actually exist here. Worse, the task was allocated at a high fame level so pretty much every lord / lady will point me to this task.

Note: Just load up the save, keep should be to your right, go under. Some areas might be 'un'-revealed again, but aside from a few kobolds from those resets you shouldn't see the boss anywhere.