I've developed and installed a Mutator at the server that adds a Counter to every Creature- and ThingFactory if there is no existing counter found. I've set the messages to
CountMessage=Only xy (insert monster class name here) more to go...
and
CompleteMessage=(insert monster class name here)s are history now!
Please report any abnormalities.
NB: the plural "s" at the end of the CompleteMessage does not always build correct English, for example Devilfishs instead of Devilfishes ("Devilfishs are history now!" will be shown).