During the dark days of the Horus Heresy, the Skitarii formed the personal troops of the Fabricator General of the Mechanicum, dedicated to searching for and recovering lost technological relics throughout the galaxy. Alas, when the Martian Schism tore the Mechanicum apart and pitted rival Fabricator Generals against each other for the loyalist and renegade camps, the Skitarii were also divided and found themselves fighting either under the banners of the Emperor or those of the Warmaster.