actually I was planning on having that only B and up can suck energy out of people via talons like Iris from the gamera series.
the guys below B carry around "pods" that they use to suck the energy our of the dirt and trees. they would work for the class B and up guys riding the harvesters like horses and scouting around for humans. Also they work with the breeders to make more monsters. My character would be a Class A working for the sole Class S on the planet. I was thinking of maybe having it that they are trying to gain communication with their homeworld which is the old earth, now taken over by monsters.