So I was embarking in 40.05 (in a world with many caves of large size) and noticed that one the the civs had only one site listed, which was a cave. I embarked there to see what is there, and I found the lair contained twenty or so lair creatures and also almost a hundred dwarves, including all notable figures for my civilization. All of them are hostile except for one, who is listed as a visitor. The hostile dwarves immediately burst out fighting with the cave creatures in the lair.
All of them have military skills, so maybe this is some army or bandit behavior bug?
Edit: One of them just got promoted to Queen.
Edit: Their general has died and been replaced.
Edit: It hasn't been the dozens of hostile dwarves killing us but the one lableled "Visitor". He killed the carpenter aboveground, then wandered to the hastily dug meeting zone like a regular dwarf before slaughtering most of the war dogs and the expedition leader. I am now trying to distract the other dwarves an make a new meeing zone in the middle of the fighting to lure him to his death.
Edit: The vile, treacherous "Visitor" has killed every cave creature remaining with no injuries, though after he assaulted the new expedition leader and departed for the "meeting hall" he has been kept away from the remaining dwarves. Now to keep the surviving dwarves busy until they can be locked in so they don't try to go to the "meeting hall" themselves to meet their end...
Edit: Things have quieted down some. The cave creatures are either dead or cowering in terror (and oddly being ignored by the cave dwarves for the most part). The murderous "Visitor" sits in the meeting areas as they are assigned, slaying any cave creatures nearby. Two of the initial seven are dead, one is unconscious from falling out of a tree but appears stable, and the rest are working more or less normally.
Edit: It seems that ONLY the "Visitor" is actually hostile; one of the wrestlers labeled "Hostile" wandered into the stairway that was dug next to the cave (to avoid the aquifer) passing several of my dwarves without issue.
Edit: Things are fairly calm now. The friendly "Hostile" dwarves wander in and out of the stairwell at times, and the hostile "Visitor" is contained in his meeting place among the "Hostile" dwarves, which he does not appear aggressive towards. I am building a cage trap to see if the "Hostile" dwarves are cage-able and digging a dry moat around the map edge. I am curious what will happen when the caravan or migrants are scheduled to arrive...
Edit: Next post for Summer.