Second Founding
The Horus Heresy proved that, despite the Emperor's efforts, the Primarchs were not perfect; they could easily be led astray and fall to Chaos.
In order to prevent one man from gaining as much power as Horus had, the branches of the Imperial armed forces were separated, the Inquisition was founded, and the loyal Space Marine Legions were divided into Chapters of roughly one thousand Marines, in accordance with the Codex Astartes.
The Second Founding was not universally accepted; the Space Wolves and Imperial Fists in particular objected to dividing their Legions, and the Imperium was nearly torn apart by another civil war. For better or for worse, Leman Russ and Rogal Dorn finally relented, although the Space Wolves and Black Templars have since grown their numbers to many more times the usual size.
List of Second Founding Chapters
Dark Angels
- Angels of Absolution
- Angels of Redemption
- Angels of Vengeance
- Lions Sable (They were destroyed trying to apprehend several Fallen in what was later revealed to be a massive trap set by Cypher shortly before The Beheading and all records of their existence were erased to hide the involvement of the Fallen in their collapse.)
- Star Phantoms - (maybe, though this chapter definitely did exist in M31)
- Angels of Vigilance - (Again, maybe, though this one is more likely)
- According to The Unforgiven by Gav Thorpe, there were 11 total Dark Angels successors in this founding.
White Scars
Space Wolves
Imperial Fists
- Black Templars
- Crimson Fists
- Excoriators
- Soul Drinkers (sort of, it's a long story)
Blood Angels
Iron Hands
Ultramarines
- Aurora Chapter
- Black Consuls
- Doom Eagles
- Eagle Warriors
- Genesis Chapter
- Inceptors
- Iron Snakes
- Libators
- Mortifactors
- Nemesis
- Novamarines
- Patriarchs of Ulixis
- Praetors of Orpheus
- Silver Eagles
- Silver Skulls
- White Consuls
Salamanders
None, as there weren't enough Salamanders left after the Horus Heresy to fill one Chapter, let alone two.
Raven Guard
Grey Knights
The Grey Knights were not created from any of the Space Marine Legions, as their gene-seed was specially created by the God-Emperor of Mankind himself and their founding members were hand-picked by Malcador the Sigillite; many of them were loyalists who had formerly been a part of a Traitor Legion (e.g. Nathaniel Garro, Garviel Loken, and Iacton Qruze). They were founded to supply the newly-formed Inquisition with a strike force against future Chaos threats.