I just had a snatcher that tried to run away, right past the elf diplomat. It seems the elf diplomat was a fire mage, he roasted the snatcher and left a neat circle of flame expanding from my trade depot. See, not all elves are bad! (fortunately rain put it out right as it was reaching the human caravan)
Then we had a siege of undead, dead warlock warlock corpses and dead skeleton skeleton corpses and the like. Which was odd. But my musketeers and their silver bullets made pretty quick work of them. About half of them went from "undead" to "invader", which didn't really change anything. I'm guessing that was the good biome resurrecting them and none were friendly races, so they still kept attacking.