Most references in the histories of the Imperium to its deeds during the accursed times of the Horus Heresy have actually been expunged.
The Renegades were defeated in a battle that destroyed the Dark Angels' Legion homeworld, Caliban, but many of the Traitor Dark Angels survived to be cast through space and time by the direct intervention of the Chaos Gods.
These survivors are known to those few Dark Angels granted knowledge of their existence as the Fallen Angels or just The Fallen.
In the eyes of the Chapter's leaders, there is only one way that the Chapter can ever atone for its shame, restoring its honour and trust in the eyes of the Emperor -- all of the Fallen must be found and either made to repent their ancient sin, or slain.
Angels of Absolution, Angels of Redemption, Angels of Vengeance, Lions Sable (Destroyed), Angels of Vigilance (Suspected), Consecrators, Disciples of Caliban, Guardians of the Covenant, Knights of the Crimson Order, Persecutors of Darkness, and the Star Phantoms (Suspected) Caliban (Destroyed); now the mobile Fortress-Monastery known as The Rock, Terra (Tertiary Rights in Abeyance), unknown number of void outposts & watch fortresses, including Skarasan Deep & Mausolia Angelis "Since the founding of their Legion at the birth of the Imperium, the Space Marines of the Dark Angels have been dreaded by their enemies and held in awe by those they protect.
Stubborn and relentless in battle, ever vigilant and zealous in their pursuit of their duties, the Dark Angels are among the Emperor's most faithful servants. For ten millennia the Dark Angels have harboured a sinister secret, an act so terrible and shameful it threatens everything the Dark Angels hold most dear – and may yet bring them eternal damnation." The Dark Angels are considered amongst the most powerful and secretive of the Loyalist Space Marine Chapters.
They were the I Legion of the original 20 Space Marine Legions to be created during the First Founding of the 30 Millennium.
Though they claim complete allegiance and service to the Emperor of Mankind, their actions and secret goals at times seem at odds with that professed loyalty, as the Dark Angels strive above all other things to atone for an ancient crime of betrayal committed over 10,000 standard years ago against the trust of the Emperor during the time of the Great Crusade and the Horus Heresy.
The Dark Angels stand first amongst the Space Marine Chapters, as they have done since their very inception as the I Legion.
They are a proud Chapter, with traditions and rituals that date back to the earliest days of the Imperium of Man.