Summoning the soul/spirit of the Raven Lord, Corvus Corax wasn't too complicated with the inherited magical knowledge I had. It's biggest issue was the amount of magical/spiritual energy required to get Corax's attention and then provide him a passageway to get to reality from the Warp.
Hence I was using the built up divinity, and faith energy within the Emperor Statue I had in the Holy Sanctum, as in theory. Corax would recongize his fathers pyschic signature and woudn't be... As hostile, hopefully after we summon him.
The ritual itself wasn't anything outstandingly heretical or even debased as one Custodian even grumbled about how the Mechanicus typically made much more of a mess with their rituals to turn on a Knight, let alone one of the larger Titans.
The ritual consisted of three aspects such was it's simplicity, a conduit to Corax himself in a drawing of a raven and of himself I drew myself. The Emperor statue that acted as both battery and a nexus. And lastly the ritual circle itself I drew onto the ground.
I took a deep breath as I had finished the ritual circle and now it was up to 'fate' now. On whether or not I get torn in half by Warp infused power claws.
"Oh Raven Lord, hear my call." I spoke with my flakes of divine energy from being a Traveler filled the ritual circle and like a spark hitting a pool of flamable heavy gas. The ritual flared to life as I continued to chant with the Custodian's visibly readying themselves.
The room darkened as blinding shadows filled the corners even as the Emperor's statue grew ever brighter his eye's becoming blinding holy spotlights that watched my form and the ritual.
Then the calls of a haunting symphony of ravens filled the Holy Sanctum threatening to ruin the ritual with the deafening screams of the birds screaming melody.
Abruptly, the screams of the raven's died out as the ritual circle's blinding radiance dulled to merely a bright glow that you could actually look at without safety equipment.
Now... Normally a person would think that the ritual failed, as no one had teleported into the ritual circle or anything. But from the moment the crows and ravens sang. I knew Corax was here.
"Lord Corax, Lord of the Fourteenth Legion. I bring word of where the Word Bearer's Homeworld is in the Warp!" I called out as I saw the shadows within the room shifting.
My words made the shifting shadows pause and then the Custodian's snapped to attention as I felt a fucking massive power claw gently pressing into my chest with Corvus Fucking Corax coming out of his invisibilty bullshit right in front of myself.
His head was turned into a massive raven's head and I swallowed my instinctive reaction to throw all my Sol flames into his his form as I registered is Ravenlord's themed armor that covered him along with his signature jet pack on his back that were enhanced by large raven wings as well.
He opened his mouth and it was sharp and painful to the ears as his... 'Primarch' aura fell onto my shoulders like a mental shroud telling me to obey, fear, and venerate the figure before myself.
"Speak... Sorcerer." Corax spat with a twitch of his large claw that moved away from my chest.
I swallowed and battling the heavy Warp infused essence which was so far beyond the demons I had seen upon the Hive World Teritum. I worked up the ability to speak.
"Lorgar and the rest of the upper ranks of the Word Bearer traitor legion has taken to working their fell magic's and meditations upon the planet Sicarius. I have a plan to kill Erebus and-"
There was a pause before Corax hissed darkly. "Erebus! That wretch still lives? No, where is Lorgar sorcerer!?" He demanded with his aura a dark shroud that demanded me to speak now.
"The entire Word Bearer legion is on that planet, Lord Corax. Lorgar himself is hiding on the planet and has been spending millenia on there in deep meditation on the nature of the Four within the Warp."
There was a long pause as Corax stared at me then his eyes slid to the Custodian's who impressively didn't even manage to flinch at the looks even as they held their Guardian Spear's at the ready to attempt to save my life.
Then he looked back to me and said bluntly. "You plan to use me as a distraction for you to what? Kill Erebus only for him to get brought back to life by the four within the Warp?"
I shook my head and said firmly. "No Lord Corax, I plan to capture Erebus's soul and then destroy it while you act as a distraction. And then after I killed Erebus, and the Four's attention is split between me and you. Several Exterminatus tier weapons will blow up the planet as we go our seperate ways."
There was a glimmer of something in Corax's eyes as he seemingly saw that I actually had something of a plan in mind then he shifted with a flurry of ravens breaking apart from his form with his form breaking apart totally into a swarm of raven's that merged into the shadows.
"Make your way to Sicarius then. I will play my part when the time comes, and the only reason I am going along with this plan. Is the fact that my father's Custodian's are following you." Corax's voice filled my mind as he had dissapeared from my perception of the world.