I propose a challenge: come up with a thematically driven herald that begins the game by spawning some sort of monster type that is heavily amplified.
I.e. create a Dracula herald (featuring the Vampire). Or make something using The Servitor of The Elder Gods. Or really any sort of monster that you enjoy and would like to pump up with story and steroids. I've already done something like this with two of my heralds. One highlights Rat-things, and the other Wraiths. If no one takes me up on this, I'll probably end up making something for the vampire or the servitor.
Good luck :')
-Avi