Nathaniel Garro - Siege of Terra: Shortly before the start of the Siege of Terra, Garro and the Knights-Errant under his command had been deployed across the Throneworld to fight outbreaks of daemonic infestation and Chaos Cultist attacks that increased in severity as Horus' Traitors approached the Sol System.This included one such brutal fight against on the Terran techno-nomad settlement known as the Walking City and later at the White Mountain, a subterranean fortress on Terra where Malcador the Sigillite ordered a group of Sisters of Silence who had been captured and tortured by the forces of Chaos and then recovered by the Loyalists to be held while his researchers sought to determine what had been done to them.In both of these combats, Garro and his Knights-Errant were forced to face an old foe, the Nurglite Daemon called the Lord of Flies who had once possessed Solun Decius and fought Garro on the airless surface of Luna. The Daemon was defeated once more and cast back into the Warp, but at a high price, for the former World Eater Knight-Errant Macer Varren was slain at the White Mountain by his comrades when the Daemon tried to possess him.As the Traitor fleets emerged from the Warp into the Sol System to begin the siege of the Throneworld, Malcador chose nine of the Knight-Errants to take before the Emperor Himself to gain His approval as the founders of the new Astartes Chapter to be known as the Grey Knights. But one of them, Garviel Loken, refused the honour so that he could gain revenge upon Horus and his former battle-brothers among the Sons of Horus.The remaining eight Knights-Errant were then taken through a Webway portal in the Imperial Palace to the fortress-monastery that had been prepared for them on Titan, the moon of Saturn, to begin their new mission.Lacking any psychic ability, Garro was not among those chosen to go to Titan and take up the new role. So Malcador instead released Garro and all of the remaining Knights-Errant who had not been chosen from his service.This was so that they could face Horus and the Traitors on their own terms in the Siege of Terra, serving no master but their desires for honour and vengeance.Alongside his old comrade Helig Gallor of the Death Guard and Loken, Garro decided to join in the defence of the Imperial Palace. Once the siege began, Garro and Loken led kill-squads that ambushed the forces of the Sons of Horus who were seeking to penetrate the Saturnine section of the Imperial Palace's Ultimate Wall that possessed a shortcut into the Inner Palace.The Traitors believed there was a weakness in the Palace's physical and spiritual defences beneath the Saturnine wall section, but this was in fact a trap that had been laid for them by Rogal Dorn as the Praetorian of Terra.In this combat, Garro and his team defeated Captain Falkus Kibre, who commanded the Sons of Horus' elite, black-armoured Justaerin Terminators. After cutting Kibre in half with his great sword Libertas, it was revealed that Kibre had become possessed by some sort of daemonic entity which fled the Terminator's body once it had been mortally wounded. Garro his expressed pity for the Possessed Traitor Marine as he finished him off.Next, Garro, Loken and their comrades faced First Captain Ezekyle Abaddon himself alongside the Blood Angels led by Captain-Paladin Bel Sepatus and the Loyalist World Eater commander Endryd Har. The Blood Angels and Endryd Har had succeeded in ambushing Abaddon's Sons of Horus, though the first captain managed to slay both Sepatus and Har in the ensuing fight.However, it took Abaddon seven kill-strikes to finally slay the monstrously strong World Eater. Trapped beneath Har's great muscled bulk after his death, Abaddon would have been slain by Garro had he not teleported away before the Death Guard could reach him.