According to Blade Devil lore, this group of Hunters come from a colder and snowy area of the Blade Devil world, where a stone city exists on the side of a cliff.
Volumes 1 and 2 will be available again once all backer orders have been fulfilled. For now, why not take a look at the trailer for Vol.2:
https://www.youtube.com/watch?v=xHLwxEQsYIM