Okay so I'm trying my hand at an omake:
The Emperor Muses
Upon Terra, the Master of Mankind watched as His true Chosen strode through the Path He had given him. Ciaphas Cain, were He still in charge, would be placed as His second- Third, if Malcador was alive at that point. For he had a gift- a power that He had feared lost.
He had common sense.
Cain thought himself a self-serving coward because he had the common sense to survive whatever the Dark Powers threw at him. He thought that his choices were dumb accidents or luck. Not so much. His Soul belonged to Him. He had seen Cain though the Schola, and waited for Him to become a Hero of the Imperium.
But things changed. They always did.
Tzeench had tried to throw Ciaphas off of the path he should have walked. Sent him to a world of nobility and vice, where the Commissar's self-claimed cowardice would trap him there.
Tzeench hadn't known that he was setting Cain up for even greater things.
The Commissar was a bomb in the corrupt world he landed on. The governors, who He despised with all of his heart (Something He and the gods of Chaos save Nurgle agreed upon- that family was pure evil) had amassed a great many forces against them. Unfortunately, most were cults to the Cancers in the Warp.
But Cain united them. By sheer accident (At least, from Cain's view), he had brought all of them under his banner. The final spark was when Ciaphas accidentally gave Emili a powerful soulstones. He would later explain it away as trying to kill her, but in actuality it had been a bribe- a bribe to Slaanesh to let her go, so he could save her from the Prince.
Instead, it solidified Emili's obsessive, yet pure, love. And that was something Slaanesh had not seen in a long time. Emili had Ascended to Daemonhood with ease, and Cain's rebellion soon began.
The first phase had gone off flawlessly. Then, the second phase began.
Ciaphas had done the opposite of what the rest of the Imperium had done in an attempt to slow down the planet, still convinced that he had to save the planet from Chaos. Instead, what he had done was something He would be kicking Himself for not thinking of it first… if He could move His legs.
He began to poison the gods themselves.
His edicts, his accidental propaganda, and his freedom of religion had turned the planet's cults to ones that He would have been reluctant to destroy- cults that performed genuine good. Instead of murderous orgies, the cults of Slaanesh made it their duty to ensure the happiness of the people. Instead of schemes that would bring down peace, the cults of Tzeentch plotted how best to make the planet run more smoothly. Instead of murderous slaughter, the cults of Khorne fought with the strength of their god, but tempered by their drive for justice, and the intense training Ciaphas put them through. The gods fed on this worship. Slowly but surely, He had felt the changes.
Already, there had been charities set up in His name, though the occupants were cultists of Slaanesh, the musings of the Prince about this new, renewable source of energy catching their ears. Several Hive Worlds suddenly began to run more smoothly, hidden saboteurs suddenly deciding to focus more on the hope they brought, and the positive change. And in many planets, Khornate worship had sprouted in the PDF, and even in secret with the Guard… yet they never turned on the Imperium. Rather, they fought to protect those they loved, and used training to smother their desire for blood and fighting.
And then… there was the Panacea.
Even had Cain been a Chaos Warlord- even if Can had performed mass sacrifices- He would have bargained for Cain's autonomy during the Great Crusade for that STC.
Nurgle had sought to destroy all of them, and damn near succeeded… but Emili, a Daemon Prince, had handed it to her beloved. And then… Cain did something that even had he turned his back on Him fully, He would have pardoned him immediately.
He gave the Panacea to the Imperium.
Amerbly Vail had been smart, spreading the STC's copies around so that those in power could not hoard it. Already, Chapters of Astartes were using them. Imperial Guard regiments had begun to see a trickle of the substance. And, just weeks ago, the Custodes had applied some to Him. It hadn't healed him entirely, but He felt a few cells regrow- He had felt His body beginning to recover. A small patch of fresh, healthy cells on a human like Him was enough to slowly begin to regenerate, provided more of the substance was used. He had, with all of His strength, sent such a message to His Companions. It had been added to the wash they used to keep Him from rotting fully. He felt stronger- more able to commune with His people- and able to provide more power to those who were worthy, and smite those who were not.
Oh yeah, there had also been Cain's killing of Karamazov. That soul He had thrown to Emili and Slaanesh. The military 'leader' in charge of that ground massacre was also thrown to the Warp. He didn't care to think about that man. Instead, He looked at the Warp, and the subtle changes, and wondered how much Ciaphas knew about the changes. If Ciaphas died, and appeared before Him (and that was a BIG if- odds are that he'd Ascend before that) He would tell the man what his contributions had wrought, and pardon him of everything… before telling him to have fun with his Daemon Princess wife.