Codex Supplement: Salamanders wrote:At the time of Vulkan’s coming, seven ancient tribes known as Great Houses wielded power on Nocturne, and under his leadership and protection they united. To honour their fealty, Vulkan organised his Legion into seven Great Houses also, each forging bonds with one of these kindreds. To this day the Salamanders Chapter retains its unique structure of seven companies – each is still known as a Great House and maintains ceremonial ties to a settlement on Nocturne.
While the Salamanders’ squad-level organisation closely follows that espoused by Roboute Guilliman’s epic treatise, their companies are larger than those in a truly Codex-compliant Chapter, each comprising twelve squads to better withstand the attritional pressures the Salamanders often face in war.