"Ah!" Sanguinius screamed. Rather than stirring Horus's tenderness, it only heightened his pleasure.
After accepting Slaanesh's power, Horus's pursuit of pleasure only grew more extreme. Before long, even tearing apart wings no longer amused him.
He looked at Sanguinius lying on the ground, covered in bloody feathers, and immediately had other ideas.
He gripped the angel's throat tightly, refusing to let go even as Sanguinius's face turned bluish-purple from suffocation.
Then he drove a heavy punch into Sanguinius's abdomen, making him immediately vomit up all the food he had eaten at the banquet.
Soon, Sanguinius was reduced to something resembling a lump of rotten flesh, yet Horus still did not stop. He quietly listened to the faint breathing within that mangled mass and ordered the daemons to organize a grand sacrifice to Slaanesh himself.
After the horrific ritual, Sanguinius was reborn. He returned to his original appearance, but his strength had not recovered, leaving him able to launch only feeble counterattacks against Horus.
"We still have plenty of time... my dear..."
Horus tightly grasped Sanguinius's wrist and led him into the debauched palace Slaanesh had specially provided.
Through glimmering tears, Sanguinius watched the Primarchs retreat from the planet.
Amid endless decadence and torment, Sanguinius called out in his heart for his father's help.
From then on, the Great Crusade headed toward a disastrous end. The blazing fire ignited by Horus plunged the entire Imperium into suffering.
Even though The Emperor personally slew Horus, he himself was struck down by the schemes of the Four Gods, becoming a half-dead skeleton who could only sit upon the Golden Throne and look on indifferently at all the suffering of the Imperium of Man.
As for Sanguinius, he went mad beneath Horus's training and torture, wandering among the Dark Gods and begging for ever