Event · M37–M38
Twenty-Third Founding
The Twenty-Third Founding is one of the numbered Foundings by which the Adeptus Astartes raised new Chapters under Terra’s sanction during the thirty-seventh. Like every Founding after the Second, it followed the pattern set down since Roboute Guilliman’s reorganisation of the Space Marine Legions: candidate gene-seed, drawn from an established parent Chapter or held in reserve by the Adeptus Terra, was apportioned to new formations of roughly a thousand warriors, each bound to the strictures of the Codex Astartes and granted a chapter world, fleet, or fortress-monastery from which to operate. The High Lords of Terra, acting through the Adeptus Astartes’ own governing bodies, held final authority over which petitions for new Chapters were approved, and it is this administrative act of sanction — rather than any single battle or campaign — that defines the Founding as a event in Imperial chronology. As with many of the later, less chronicled Foundings, the full roster of Chapters raised in the Twenty-Third Founding is not uniformly preserved in surviving Imperial record, and accounts of which formations trace their gene-seed and heraldry to this particular Founding differ between archives. What is consistently attested is the broader context: by the thirty-seventh millennium the practice of Founding new Chapters had long settled into an intermittent rhythm, undertaken to replenish losses, extend the Adeptus Astartes’ reach into contested or newly reclaimed sectors, and answer the perpetual demand of the Imperium’s wars across its many fronts. The Twenty-Third Founding sits within this pattern as a marker of continuity rather than of singular crisis, its Chapters dispatched from Terra’s authority to garrisons and campaigns whose particulars have, for the most part, faded from common record. In the current era, the Twenty-Third Founding is remembered chiefly as a chronological anchor: a point against which later Chapter lineages, gene-seed inheritances, and campaign histories are sometimes dated when their own founding is otherwise uncertain. Where individual Chapters can be shown to descend from this Founding, their subsequent service forms part of the wider history of the Adeptus Astartes and its parent Chapters; where they cannot, the Founding itself remains a recorded but sparsely detailed step in the Imperium’s long effort to sustain its Space Marine strength, its place fixed on Terra as the seat from which such sanctions were, and are, given.
See where Twenty-Third Founding occurred on the galactic map in the 41st Millennium.