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Soon enough, the Emperor took the bait and He alongside [[Rogal Dorn]], [[Sanguinius]], [[Constantin Valdor]], and their elite forces all teleported to the ''Vengeful Spirit''. It was then that Horus sprung his trap, using his sorcerous connection to his flagship to scatter the loyalists throughout the vessel. He took control of many of the Emperor's own Custodes, forcing them to attack their own liegelord as the Emperor reluctantly struck them down.{{Fn|28d}} Rogal Dorn was trapped in an endless desert of madness for what seemed to him to be centuries.{{Fn|28e}} Horus revealed his true power and mental strength, which had apparently been concealing in order to lure his father to him.{{Fn|28f}} According to [[Actae]], Horus was preparing to be elevated to a fifth [[Chaos God]], using humanity just as [[Slaanesh]] had used the [[Eldar]]. All across Terra, his followers chanted the name of the soon-ascendant [[Dark King]]{{Fn|28g}} (though apparently this in fact referred to the Emperor).{{Fn|28g}}

Eventually Swelling with the powers of Chaos, the fully awakened Horus drove the crew of the ''Vengeful Spirit'' mad with his mere presence including hardened Space Marines such as his equerry [[SanguiniusKenor Argonis]].{{Fn|29a}} He broke down the barriers of space and time between the surface of Terra and his flagship, Primarch of causing the two locations to overlap with one another and for time itself to be paused at this single monumental moment, which even the [[Blood AngelsInevitable City]]manifesting in his honor.{{Fn|29b}} Still preparing to face his father, appeared before Horusdeliberately let [[Sanguinius]] reach him within the heavily mutated [[Lupercal's Court]]. Planning to turn Sanguinius to Chaos so that they may confront their father together, who offered Horus was genuinely disappointed when his brother refused his offer to join him riches in ascendency.{{Fn|29c}} Instead, the already heavily injured Sanguinius attacked Horus with all his might, displaying ferocious combat ability. Horus was genuinely disappointed and still held back his true power if , engaging in a purely martial battle with Sanguinius in hopes of breaking him down so he denounced may accept the powers of the Warp. However Sanguinius fought so stubbornly and viciously that Horus grew frustrated and even took several wounds.{{Fn|29d}} In the end, Horus was forced to change his allegiance to plans when he detected that the Emperorwas incoming towards his location. Horus finally decided to kill Sanguinius and unleashed his full power, reaching into the 8th dimension to grab Sanguinius refused and attackedslam him to the ground mid-flight. Horus killed proceeded to batter his brother with ''[[Worldbreaker]]'' and impaled him several times with his [[Talon of Horus|Talon]] before the skull of [[Ferrus Manus]]. Horus let out a disappointed sigh as his brother died and was found standing over his broken body when the Emperor entered the chamberwas strung up by Daemons.{{Cite ThisFn|29e}}

Shortly after killing Sanguinius, Horus was confronted by the Emperor. The Emperor and Horus fought with a power that would have eviscerated any mortal man dozens of times over with each blow. The Emperor held back for much of the battle, remembering Horus as his beloved son and not wishing to believe that he had turned so utterly to Chaos. This allowed Horus to inflict crippling mortal wounds on the Emperor, since nothing short of the Emperor's full power would be sufficient to defeat him. At the critical point in the battle, a lone [[Adeptus Custode]] guard entered the room (while others state the lone warrior to be [[Ollanius Pius]], an [[Imperial Army]] soldier). Horus flayed him alive with but a look and in that instant the Emperor realised how far his favoured son had fallen. The sacrifice of the Custodian bought the Emperor time to deliver a finishing blow to Horus. With iron resolve, he gathered his full strength and delivered a massive psychic blow that killed Horus almost instantly and obliterated his very soul. In his final moments, the powers of Chaos were driven from him and the Emperor sensed his favoured son's return to sanity for a fraction of a second before he finally died.{{Cite This}}