Part Four - The Last Custodes
Legends tell of a glorious and holy few, the Custodians and Praetorians of the God-Emperor himself. This legion, blessed with the task of guarding the Emperor, has watched many events unfold, even as they stood unmoving for thousands of years. More powerful than your typical Space Marine or even the now-lost art of the Primaris Astartes, these golden warriors had waited for their eternal master to stand from his throne again.
Ironic, it was, that when he finally did, few Custodians remained to see it. The Second Siege of Terra burnt Humanity's system of origin with not the intent of conquering, but of total destruction. Even as the mysterious allies the Emperor had summoned to his aide arrived in defense of Humanity's realm arrived, entire moons had been shattered and whole planets wiped of life.
While the Solar System was filled with pockets of resistance and centers of military strength the monster that replaced Abaddon could not justify fighting, none was more defended or alluring to the Chaos Gods' new champion than that of Holy Terra. Daemon Engines, Ghost Fleets, and ten Traitor Legions descended upon the cradle of Humanity, and the sun itself was blotted out by the ships of Imperial and Chaotic decent dueling or the various Warp Storms providing instant reinforcements.
It is a testament to the power of the Adeptus Custodes that they even lived to see through the end of the Second Siege, where Space Marine Chapters went extinct, Gods died, and the Primarchs waged their final battles. While the name of the Last Custodes is unknown, as are the figures who stood in defense of the Emperor during the Immaterial Regicide that bookended the Imperium's bloated life, all that is known is that there was a Custodes, and if myth is to be trusted, still is.
Some suspect this golden warrior to have been Constantin Valdor, an ancient hero of the Horus Heresy who returned in time to save the Emperor from certain doom in the face of victory eternal. Others suspect Trajann Valoris, the last Captain-General of the Adeptus Custodes. The more heroically inclined tellers of these tales speak of just another Custodes being the last to stand guard, certainly a mythical status but not that of a pre-defined hero.
Whatever the name of this Custodes is, his service in the final battle was undeniable, though his deeds in specific are often clashing with other heroes, like a flame-wrapped Primarch, a member of the Grey Knights, another flame-wrapped visage, this time of a guardsman, or Rogal Dorn himself. Nevertheless, most storytellers end his story with his continued survival past the Emperor's own sacrifice, though some do prefer the idea of a noble sacrifice to mirror the Emperor's.
Still, if his survival is truth, then it would explain a myriad of mysterious occurrences; many settlements attacked by the dangerous Tau Empire, the Ork hordes, or the Chaos Space Marines clinging to their dead gods have been defended and protected by a single golden hero, before moving onto other places to stand praetorian once more. Those storytellers bold enough speak of the Emperor's last words to the Custodian; "Your duty is not over, for in all Humanity, I am, and you are to defend me until the last threat is vanquished."
Or so the storytellers say.