Today I had a lesson in transitive member/enemy status.
I created a human swordswoman, recruited two human macemen from the local town, and went on a grand adventure across the world. We killed hundreds of wolves, bears, giant scorpions, lions, and other wildlife as we wandered across the world. I stopped at a elvish civilization on the other side of the world, talked to their leader, and ended up killing a handful of megabeasts - assorted hydra, dragons, ettins, cyclops, and other tough yet killable megabeasts. Eventually the Elves ran out of jobs for me. I continued wandering across the world, eventually returning to my home civilization. I killed a few more monsters for the local ruler, then retired my adventurer in her starting town.
I then created an axedwarf at a mountainhome nearby. I traveled to the Elvish nation and went on a killing spree. After killing a few hundred elves in several different cities, including the queen and head druid, I went wandering over to the human towns. Initially the humans I spoke with were friendly to me. I encountered one of the macemen who had accompanied my previous adventurer, and he was glad to tell me of all the creatures he'd killed.
Then I ran into my previous adventurer. She immediately called me out, boasted of the monsters she'd killed, and told me to prepare to die. I hadn't attacked her, but it seems that murdering all those elves she'd been on good terms with had made me her enemy. I tried to run, which was when I discovered that every human in town was now hostile. When the beloved hero of two civilizations calls you out as an enemy, everyone listened. I didn't make it far before a hail of crossbow bolts crippled me, then my former adventurer caught up and killed my current adventurer easily.
Kind of a neat feature, I didn't know that the game carried over alliances between adventurers and civilizations this way. Now I need to figure out if I can manipulate this to get two civilizations to be at war with each other.