This also happened to me and I think there might be some sort of invisible "Troll Warrior" somewhere. I received a "taunt" message from one and none of my units or cities where adjacent to one, nor could I see a single one on the cloth map or the regular.
After ridding the Wildlands of enemy units, I moved on once nothing happened, but left three Pioneers standing by inside the Wildlands, just in case. A dozen turns later, I set an offensive unit to move through the Wildlands on its way to another destination, and I got one of those pop up "taunts" from an NPC, a "Troll Warrior" telling me to stay away from his stuff.
I looked at every single city and unit on the map and I was not adjacent to any enemies that I could see. The Wildlands was a Morian one, which had had Troll mobs. I perched on every notable square I could identify on the cloth map, but the Wildlands ZOC never dispersed and my next step is to make a line of units and "sweep" it from the north of the Wildlands to the south to see if a battle starts.
I'm playing as Tarth, so NPC monsters don't attack me.
