Twice today different AI monster units foraged through the rear area of an AI empire. This was a portion of the map previously unrevealed to me, but it became visible as the monsters marauded across the countryside. Full details became exposed as if the monsters belonged to me, which they did not.
This happened to an AI player that I recently started trading with but had no other political arrangements. Also I believe the monster units were recently spawned in as part of a small wave of baddies that landed in the vicinity and then started roaming. Can't swear to that though. Coincidentally both units were Ignys's Army. It's possible that one or both of the monsters had previously squashed a trading caravan along the way. Again, can't swear to that. I really started to pay attention when the cloth map began lighting up and I knew all my units were home tucked safely into their beds.
As my unwitting spies gave me a good peek at what my opponent was up to, I got to thinking that this could have the makings of a handy little spell: "Bug a Roaming Monster - Reveals to you all details of the map explored by the monster."