The Brothers Penitent is one of the Loyalist Space Marine Chapters founded as part of the Astartes Praeses -- one of the 20 Chapters of Astartes mentioned in the ancient tome known as the Mythos Angelica Mortis that was created to defend the regions surrounding the Eye of Terror in the Segmentum Obscurus from the Forces of Chaos. The Brothers Penitent are of an unknown Founding and origin. Though this Chapter works alongside those of the Astartes Praeses, it has a reputation for being insular in nature.