My avatar is from the chilren's game Monster Mash
This refers to monsters you are facing in combat. In general you can always figure on 'enemies' or 'opponents' meaning the opposing force in combat.
Thanks for the answer!
Combat with other players' parties lacks the 'when monsters are revealed' trigger. I don't recall exactly what trigger that weapon uses.
Actually I think the actual trigger was, when a battle starts or something... I'm not sure...