They hunt hollows and stuff and are split into three categories
Hunters/Trackers/Researchers
Hunters: Hunt the hollows and kill them. They collect their souls for the researchers, khon labratory or soulguards
Trackers: They help alongside hunters, analysing the area of the hunt and giving instructions for the best moves to do. Also help newbies.
Researchers: They keep track of the souls and experiment with them to see what kills the hollows best and research different methods for hunting. They also are trainers for hunters.