By the the final stages of the Siege of Terra, Caecaltus alongside fellow Proconsul Uzkarel Ophite were the two sentinels closest to the Emperor directly on the steps of the Golden Throne. Upon the rousing of the Emperor to confront Horus aboard the Vengeful Spirit, Caecaltus was chosen by the Emperor to accompany Him in the teleportation assault. Before Malcador the Sigillite took the place of the Emperor on the Throne, he put his finger in his mouth and made his sigil with saliva upon Caecaltus' armour.[1a]
Upon the teleportation aboard the Vengeful Spirit, Caecaltus succumbed to the Warp-sorcery of Horus alongside dozens of other Custodes. The Companions were then controlled by Horus into attacking the Emperor, blood flowing from their eyes at the effort to resist. Caecaltus was amongst the Custodes to survive the ordeal, and the lingering taint of Horus was expelled from him by the Emperor. However the shame of attacking his Master will never go away.[1b]
Dusk continued to accompany his master even as out of desperation, the Emperor began to drink from the Warp and transform into an entity dubbed the Dark King. This proto-god swelled with power to an extent that His very presence killed all Custodians around him save Dusk, who apparently had survived due to Malcador's earlier blessing.[2a] However Dusk was still a near-totally charred corpse, and acted as little more than a mouthpiece for the Emperor during His conversation with Ollanius Persson. After being convinced by Persson to abandon the power of the Dark King, the Emperor let out a blast of power that managed to heal Caecaltus.[2b]
Dusk, alongside Leetu, Garviel Loken, and the Emperor Himself ultimately faced Horus within Lupercal's Court aboard the Vengeful Spirit. After Horus grievously wounded the Emperor Dusk briefly stood between the traitorous Warmaster and his King. Defying Horus, Dusk was contemptuously hit with a blast of dark energy emitted from the Warmaster's great eye upon his breastplate. Much to Horus' shock Dusk survived, apparently due to the sigil Malcador had left upon him. Frustrated, Horus was able to gleam all 610 names Dusk had collected and used it to gain absolute power over the Custodian. Horus quickly recited all the names then let out a second blast that obliterated Dusk utterly.
- 1: The End and the Death: Volume I (Novel)
- 2: The End and the Death: Volume II (Novel)
- 3: The End and the Death: Volume III (Novel) - 10:vi