Really great theme for this faction! I think the Devourers have the direct opposite motivation to my faction ;-) I think "Havoc" is the right word for the action because this faction seems primed to wreak havoc on the map.
Just curious what your thinking was behind the Heralds? At first, I assumed the Swarm would have to move to a clearing with a Herald (as a way to "announce the coming arrival" of the Swarm). But it seems like they're just buffed up warriors?