A/N: Hey there! Hope you enjoy the story.

This fanfic account is now shared between two authors. This story is the debut of the second author associated to this account.

Chapter 1: The Heresy

The Emperor was Humanity's shining light in the darkness. Humanity was a race long on the edge of extinction and annihilation at the hands of Daemons, Xenos, Mutants, Psykers, and Heretics on the inside. For millennia, Mankind had suffered and laboured simply to survive the cruel, black future of the Age of Strife. When greeted with the seemingly endless wisdom and power of the Emperor of Man, the godlike being became somewhat of a father to the Humans of the Milky Way. From Terra to the edges of the known universe, Humankind came to love the Emperor for His Great Unification or hate him as a tyrant; the latter in secrecy or in fiery death. However, the much adored inhuman saviour that was the Emperor, gold-clad essence known in every heart and mind that could call itself Human, was not without his imperfections; his demons.

It was in the months immediately following the Triumph of Ullanor, while war raged in the Akum-Sothos Sector, that it truly began. Magnus the Red, the Crimson King of Prospero and Primarch of the XV Legion of Astartes, sat in his quarters aboard his Sons' capital ship after the subjugation of another enemy of the Imperium of Man alongside his brothers Lorgar and Leman Russ, the latter of which he was desperately trying to avoid. As the XV Legion's fleet glided through the void of deep space, he felt it: dread, fear, a sudden, thick uneasiness that fell upon him like the armoured foot of a Titan. He winced as the sudden assault on his emotions physically startled him, and he shot up out of his seat immediately. He must warn his brothers, something is wrong. Something is wrong with their father.

Corvus Corax, Liberator of Kiavahr and Primarch of the XIX Legion, was upset, to say the least. In the midst of pacifying the Akum-Sothos Rebellion alongside his brothers Leman Russ of the VI Legion, Perturabo of the IV Legion, and Warmaster Horus of the XVI Legion. Him and his sons had been engaged in heavy combat, testing out the new Mk V "Corvus" Power Armour against the heretical rebels of the sector. It was after several hours of testing that he received a summons from Horus; who'd been placed in command of all his brothers by their father earlier that year. Corvus tried to hurry the battle, hoping to be able to pacify this particular world before Horus became impatient, and was able to achieve an acceptable victory over the following days.

When he finally went to speak to Horus, he was instead greeted by his red-skinned brother Magnus. This was the source of Corvus' discontent with the situation at hand. He'd expected to be informed of urgent news from one of his brothers fighting alongside him, or from Terra itself, not be drawn into a debate on the merit of Psykers in the Imperium. Corvus did not like Magnus, nor did he approve of his arcane powers and interests. Him and Magnus stayed in uncomfortable silence in Horus' private quarters, Magnus looking somehow rejected, worried, tired, excited and angry all at once as Corvus shot him glances, until Horus arrived to break the silence.

Horus entered the room and the silent argument between Magnus and I came to a halt. I gazed upon my brother briefly, as if to ensure it was him. Horus is a tall man even for a Primarch, as he is amongst the largest of our brothers. Magnus, however, was the tallest of all of us. This latter fact may or may not be due to Magnus' abhorrent use of sorcery, projecting himself to fit the situation. The thought briefly crosses my mind that father also does this, and I am aware that Magnus has read this brief thought, which makes me angry. Then again, father reads my thoughts…

"Corvus. Please don't antagonize Magnus, you know our brother has all the best intentions," Horus says. "Besides, it's not as if there's anything wrong with what he does, considering there's no greater Psyker than father Himself. Ask Vulkan, Sanguinius or Roboute how they feel about it, they'll tell you."

I sigh and rub my armoured hand over my face, already rather impatient with all of this. I acknowledge the validity of his points however, and I feel a tad guilty for how I treat Magnus. Maybe I should pursue a more… tolerant perception of my brother… besides, I'm not Russ or Mortarion; I won't verbally assault Magnus over the issue, especially in the presence of Horus.

I turn to Magnus and mutter "Perhaps you're right, brother." Horus nods and smiles, though I notice it is a fleeting thing, and I also notice that Magnus has maintained a small scowl ever since the first mention of father.

"So… why have you called me here? I'm sure you know I was in the middle of a compliance campaign-," Horus cuts me off.

"Magnus… has received disturbing premonitions, and he believes that you and I are the most trustworthy of all our brothers currently on campaign."

I'm quite shocked Magnus considers me trustworthy, and part of me wants to believe this is some sort of practical joke. Surely Magnus would've first told father had anything of this nature been worrying him enough to pull me out of battle and involve Horus.

Then I hear Magnus' voice in my mind, and I'm about to become annoyed once again when he speaks.

"Corvus, I need you to hear me out. I'm not going to risk a verbal argument with you putting this any further behind, so I shall simply show you the very things I felt and saw."

I internally sigh again and am then thrown back into my seat. Not by Magnus' efforts, but by shock.

Suddenly, I am no longer on the Vengeful Spirit, but rather, I am on Terra. I look around, and stagger in horror when I take in the terrifying visage. The planet-city that is Terra is burning and collapsing into dust, fire and smoke, and I see an uncountable number of warships in the sky. Some are in the colours of the IX, VII and XVI legions; the Blood Angels, Imperial Fists and Luna Wolves. The legions of my brothers Sanguinius and Rogal Dorn, and of course, Horus. Other ships are the bright gold of those directly under the command of our father. They seem to be fighting each other, and I wince upon seeing ships on both sides explode and plummet to the surface of the Throneworld.

As I continue to look around, I see battle on the surface as well. I notice the ground forces of the legion in orbit, or rather, the strewn corpses of their dead scattered throughout the rubble, alongside those of Terran civilians, Imperial Army units and… father's Custodians? I don't understand… have my brothers betrayed Mankind? Has there been some kind of revolt on Terra? I shiver when I remember my physical body is still in a room with Horus, whose sons are attacking Terra in this vision.

Then, I see it. On the foot of the Imperial Palace, I see father, flaming sword at his side. He stood over the bloody, burnt corpses of Horus and Sanguinius. I see Dorn standing opposite of Him, sobbing. His face contorted in a rare show of emotion from my most stoic brother; grief and anger. His form is covered in blood.

He raises his eyes to father, and shrieks "Traitor! We trusted you, believed you, loved you! You lied to us!"

Father chuckles darkly, and his eyes flash a deep crimson as he blows Dorn backwards with psychic power. I begin to shake with many emotions as Father then walks towards my brother's wounded and weakened form, Dorn looking at father in livid defiance.

Father then puts his sword against Dorn's neck, and says in a cruel, cold tone, "Perturabo would've put up a better fight."

I reach out and yell "No! Father, don't!" as he plunges his blade into my brother's throat. Then I awake, still screaming.

When I take in my surroundings again, I see Magnus looking upon me with regret and sad understanding, while Horus bears a concerned and unnerved expression.

"Do you see why I had to speak with you about this, and not father?," Magnus says in my head, and I blink and nod, feeling a wave of nausea come over me. I face Horus and shoot him a look that says "Have you seen this?"

He shakes his head, but says "No, but he told me what he saw. I'm… happy I didn't have to see it personally." I grind my teeth and clench my seat, looking Magnus in the face.

"What do you want me to do?"

A/N: Once again, hope you enjoyed the story :) Please do feel free to leave a review, like, or follow.