In most games units in neutral cities do not detoriate, undead or not. It's more likely that they grow.

I understand neutral as a city or a unit of mercenaries that do not belong to any "player", meaning they do not follow orders, do not cost upkeep, most likely stay passive, can be recruited (bribed, bought, hired) and defend themselves to the death. Very often neutrals have no bright color (most are gray) and when they become part of one side they are the color of the player. In a strategy game, Ansom would be the perfect guy for the white, the elves green and Stanley back.

Because Erfworld is a game world I wouldn't be surprised if GK turned gray instantly the moment the Tool croaks or gives it up. And if GK turns gray that is definitely good news for Parson.

Looking forward to seeing next strip....