Using negative creatures as guards is a great idea; I hadn't thought of that before :smile12:
It will be added to the editor!
This idea was previously discussed here:
#1923
It’s interesting, but you can do this in the standard editor. Just type a negative number into any text field and copy it into the input string in the properties of the message timer.
It’s strange that no one except the author of this map came up with this.