==Cover Description{{Fn|1}}==Having recovered from his grievous injuries, [[Warmaster]] [[Horus]] leads the triumphant [[Imperial]] forces against the rebel world of [[Isstvan III]]. Though the rebels are swiftly crushed, Horus's treachery is finally revealed when the planet is [[Exterminatus|razed]] by [[virus bomb]]s and [[Space Marines]] [[Battle of Isstvan III|turn on their battle-brothers]] in [[Horus Heresy|the most bitter struggle imaginable]].{{Fn|1}}

[[Warmaster]] [[Horus]] has fallen to [[Chaos]], but his plans of rebellion against the [[Emperor]] are known only to a few he trusts to side with him. [[Primarchs]] [[Angron]], [[Mortarion]] and [[Fulgrim]] of the [[World Eaters]], [[Death Guard]] and [[Emperor's Children]] respectively have all sided with Horus and their four Legions gather in the Isstvan system on the pretence of crushing a rebellion by the Isstvanians. The unconscious [[Euphrati Keeler]] has developed a cult following who believe the Emperor is a deity and she is a saint, [[Kyril Sindermann]] chief among them. Horus questions Chief [[Astropath]] [[Ing Mae Sing]] about the saint and afterwards Sing sends a psychic warning to Sindermann, who recruits [[Titus Cassar]] of the [[Legio Mortis]] [[Titan]] Legion and his reluctant friend [[Jonah Aruken]] to help him save her. Aruken, Cassar and Sindermann go to rescue Keeler, only to find [[Maggard]], former bodyguard of [[remembrancer]] [[Petronella Vivar]] turned genetically-enhanced enforcer for Horus, about to kill her. Maggard attacks them but becomes unable to move, the bullets from his gun moving very slowly, and the three men realize that Keeler has awoken and is using her powers to save herself and them. Before Maggard can stop them they carry Keeler to safety amidst the bowels of the ''[[Vengeful Spirit]]'''s lower decks. Horus sacrifices Sing in order to facilitate an audience with [[Chaos]] as revenge for sending the warning.{{fn|2b}}

Horus questions Chief [[Astropath]] [[Ing Mae Sing]] about the saint and afterwards Sing sends a psychic warning to Sindermann{{fn|2c}}, who recruits [[Titus Cassar]] of the [[Legio Mortis]] and his reluctant friend [[Jonah Aruken]] to help him save her.{{fn|2d}} Aruken, Cassar and Sindermann go to rescue Keeler, only to find [[Maggard]], former bodyguard of [[remembrancer]] [[Petronella Vivar]] turned genetically-enhanced enforcer for Horus, about to kill her. Maggard attacks them but becomes unable to move, the bullets from his gun moving very slowly, and the three men realize that Keeler has awoken and is using her powers to save herself and them. Before Maggard can stop them they carry Keeler to safety amidst the bowels of the ''[[Vengeful Spirit]]'''s lower decks. Horus sacrifices Sing in order to facilitate an audience with [[Chaos]] as revenge for sending the warning.{{fn|2e}} The Emperor's Children and Death Guard attack an enemy station on [[Isstvan Extremis]] where they discover a [[Warsinger]] leading the defenders. Death Guard [[Space Marine Captain|Captain]] [[Nathaniel Garro]] is badly wounded by the Warsinger's sonic power but [[Lord Commander]] [[Eidolon]] is able to kill it with his own sonic shriek. {{fn|2f}} This arouses the suspicion of [[Saul Tarvitz]], who questions Eidolon about it and is taken to [[Apothecary]] [[Fabius]]'s laboratory where he is shown the many surgical enhancements Fabius is making on legion members and offered a place in the new order. Horrified by Fabius's experiments, Tarvitz rejects the offer and leaves. {{fn|2g}} An assault force containing elements of all four legions chosen by Horus and including [[Garviel Loken]], [[Tarik Torgaddon]] and [[Lucius (Emperor's Children)|Lucius]] descends on Isstvan III's capital city and battle breaks out.{{fn|2h}}

Suspicious at the hand-picked nature of the assault force, Tarvitz talks his way into remaining in the fleet when the assault force deploys {{fn|2h}} and investigates the gun decks, where he discovers the ship's crew loading lethal [[virus bombs]] into the ship's guns. {{fn|2i}} Realizing that the marines deployed to the surface are about to be betrayed and wiped out, Tarvitz steals a [[Thunderhawk]] and flies for the surface to warn them. He is pursued by members of his own legion who are part of the betrayal and in desperation puts himself at the mercy of [[Nathaniel Garro]], who is excluded from the assault force and relegated to commanding the frigate ''[[Eisenstein]]'' due to his injuries. Garro, an old friend of Tarvitz's, believes him when he tells him of the imminent betrayal and orders the ''Eisenstein'' to fire on the Thunderhawks pursuing Tarvitz. The resulting cloud of debris hides Tarvitz from the fleet's sensors as he lands on Isstvan, Garro reporting that Tarvitz is dead before preparing to jump to the [[Warp]] and bring warning of Horus's betrayal to the Emperor.{{fn|2j}} On the surface the [[Sons of Horus]], World Eaters, Emperor's Children and Death Guard whom their primarchs deemed too loyal to the Emperor to rebel against him battle the rebel Isstvanians. The Sons of Horus' [[Drop Pods|drop pods]] scatter throughout the target area and they struggle to link up and capture their objective, the Sirenhold. Lucius leads the Emperor's Children half of the attack on the Precentor's Palace while the World Eaters under Captain [[Ehrlen]] become bogged down massacring fanatical citizens in a plaza to the north and the Death Guard advance through the city's defensive trenchworks.{{fn|2i}} Lucius succeeds in killing the rebel governor [[Vardus Praal]] and the Emperor's Children capture the palace.{{fn|2k}} Tarvitz then arrives and warns them of their imminent betrayal, tasking Lucius with transmitting a warning to the Sons of Horus and Death Guard while he goes to warn the World Eaters.{{fn|2l}} Awakened screaming by a premonition of the virus strike, Euphrati Keeler transmits the vision to Sindermann and [[Mersadie Oliton]], who realise the betrayal that is about to take place.{{fn|2k}} The majority of the Emperor's Children and Sons of Horus are able to take shelter beneath the palace in time, but few of the World Eaters or Death Guard reach the shelter of bunkers and more are killed when Horus follows up the virus-bombs with an orbital strike that ignites all the gas in the atmosphere, burning the entire planet.{{fn|2m}} Crewing the ''Dies Irae'' in support of the Death Guard, Jonah Aruken and Titus Cassar hear the command to power down and seal their machine, their princeps [[Esau Turnet]] being loyal to Horus and so having received warning.{{fn|2l}} Cassar realizes the truth after they ride out the virus strike and firestorm and attacks Turnet, pleading with Aruken to help him, but his insistence that the Emperor is a god alienates Aruken who does not believe and chooses ambition over friendship, shooting Cassar dead.{{fn|2n}}

On the surface the [[Sons of Horus]], World Eaters, Emperor's Children and Death Guard whom their primarchs deemed too loyal to the Emperor to rebel against him battle the rebel Isstvanians. The Sons of Horus' [[Drop Pods|drop pods]] scatter throughout the target area and they struggle to link up and capture their objective, the Sirenhold. Lucius leads the Emperor's Children half of the attack on the Precentor's Palace while the World Eaters under Captain [[Ehrlen]] become bogged down massacring fanatical citizens in a plaza to the north and the Death Guard advance through the city's defensive trenchworks. Lucius succeeds in killing the rebel governor [[Vardus Praal]] and the Emperor's Children capture the palace. Tarvitz then arrives and warns them of their imminent betrayal, tasking Lucius with transmitting a warning to the Sons of Horus and Death Guard while he goes to warn the World Eaters. Awakened screaming by a premonition of the virus strike, Euphrati Keeler transmits the vision to Sindermann and [[Mersadie Oliton]], who realise the betrayal that is about to take place. The majority of the Emperor's Children and Sons of Horus are able to take shelter beneath the palace in time, but few of the World Eaters or Death Guard reach the shelter of bunkers and more are killed when Horus follows up the virus-bombs with an orbital strike that ignites all the gas in the atmosphere, burning the entire planet. Crewing the ''Dies Irae'' in support of the Death Guard Jonah Aruken and Titus Cassar hear the command to power down and seal their machine, their princeps [[Esau Turnet]] being loyal to Horus and so having received warning. Cassar realizes the truth after they ride out the virus strike and firestorm and attacks Turnet, pleading with Aruken to help him, but his insistence that the Emperor is a god alienates Aruken who does not believe and chooses ambition over friendship, shooting Cassar dead. In the fleet , Horus gathers the remembrancers from the ''Vengeful Spirit'' and shows them the bombing {{fn|2l}} before ordering his men to open fire, massacring them. Kyril Sindermann and Mersadie Oliton escape alongside Euphrati Keeler when she leads them to [[Iacton Qruze]], the Sons of Horus' elderly and often dismissed third captain, who leads them away from the massacre. The four arrive at the ''Vengeful Spirit'''s hangar and plan to steal a Thunderhawk but are intercepted by Maggard. {{fn|2m}} Qruze and Maggard fight but are evenly matched until Sindermann picks up Maggard's dropped pistol and shoots him in the side, allowing Qruze to finish him off. The four steal a Thunderhawk and flee, guided by Keeler to the ''Eisenstein'' where Nathaniel Garro takes them aboard.{{fn|2n}}

Infuriated by the survival of the loyalists on the surface, Angron spearheads a World Eaters' attack wave to destroy them without waiting for Horus's orders. Angron and his traitor World Eaters assault their loyalist counterparts and Tarvitz flees on Ehrlen's orders to take command of the other survivors. {{fn|2m}} Forced to support Angron , Horus deploys the traitor Emperor's Children and Death Guard, turning what was meant to be a single wipeout blow from orbit into a protracted ground war. {{fn|2n}} Tarvitz emerges as a brilliant leader, commanding the loyalists as they repel wave after wave of traitor attacks while slowly being whittled down. Frustrated and jealous that Tarvitz is getting all the glory , Lucius slays traitor Emperor's Children [[Chaplain]] [[Charmosian]] and uses his helmet microphone to contact Eidolon, selling out the loyalists in exchange for a place among the traitors.{{fn|2o}}{{fn|2p}} Horus commits the Sons of Horus under [[Serghar Targost]] and [[Luc Sedirae]] to the battle while sending [[Ezekyle Abaddon]] and [[Horus Aximand]] to confront their former [[Mournival]] brothers Loken and Torgaddon. {{fn|2p}} Eidolon launches a devastating attack, penetrating the palace where he massacres the loyalist wounded. Receiving word of Abaddon and Aximand's arrival Loken and Torgaddon leave the palace, Loken being attacked by [[Kharn]] until a Sons of Horus' tank drives over them and impales Kharn on its dozer blades. Tarvitz finds Lucius among the corpses of loyalist Emperor's Children and discovers his betrayal. The pair fight, and Tarvitz is hopelessly outmatched until he copies something Loken once did when fighting Lucius in the practice cages and drops his weapon in favour of punching Lucius in the face. A squad of loyalists arrive and open fire on Lucius, but he manages to escape. Leading the surviving loyalists he pulled out of the fight, Tarvitz takes advantage of Eidolon's undisciplined attack and manages to repel the assault.{{fn|2q}}

Loken and Torgaddon confront Abaddon and Aximand in the ruins of the city's parliament building. The confrontation splits into two duels as Loken fights Abaddon and Torgaddon fights Aximand. Outclassed against Abaddon Loken knows he needs Torgaddon's help to win, but Aximand kills Torgaddon, leaving Loken helpless. Abaddon grievously wounds him, but before he can finish Loken off the ''Dies Irae'' steps on the building and brings the roof down. Abaddon pulls Aximand from the rubble, noting his sorrow at murdering Torgaddon, and believing Loken dead they return to the fleet. With the loyalists all but destroyed , the traitors fall back to [[Isstvan V]] and Horus firebombs the city from orbit, Tarvitz and the scant few survivors bracing for the end knowing that they hurt the traitors and bought time for Garro to reach Terra. Buried beneath the rubble of the parliament building, the last thing that Loken sees is the bombs falling towards him.{{fn|2r}}

*[[Horus]] — [[Primarch]] of the [[Sons of Horus]], [[Warmaster]] of the [[Great Crusade]]{{fn|2a}}*[[Angron]] — [[Primarch]] of the [[World Eaters]]{{fn|2a}}*[[Fulgrim]] — [[Primarch]] of the [[Emperor's Children]]{{fn|2a}}*[[Mortarion]] — [[Primarch]] of the [[Death Guard]]{{fn|2a}}

*[[Ezekyle Abaddon]] — [[Space Marine Captain|First Captain]]{{fn|2a}}*[[Tarik Torgaddon]] — [[Space Marine Captain|Captain]], [[2nd Company (Sons of Horus)|2nd Company]]{{fn|2a}}*[[Iacton Qruze]] — [[Space Marine Captain|Captain]], [[3rd Company (Sons of Horus)|3rd Company]]{{fn|2a}}*[[Horus Aximand]] — [[Space Marine Captain|Captain]], [[5th Company (Sons of Horus)|5th Company]]{{fn|2a}}*[[Garviel LokenSerghar Targost]] — [[Space Marine Captain|Captain]], [[10th 7th Company (Sons of Horus)|10th Seventh Company]], [[Warrior Lodge|Lodge Master]]{{fn|2a}}*[[Serghar TargostGarviel Loken]] — [[Space Marine Captain|Captain]], [[7th 10th Company (Sons of Horus)|Seventh 10th Company]], [[Warrior Lodge{{fn|Lodge Master]]2a}}*[[Luc Sedirae]] — [[Space Marine Captain|Captain]], [[13th Company (Sons of Horus)|13th Company]]{{fn|2a}}*[[Tybalt Marr]] — [[Space Marine Captain|Captain]], [[18th Company (Sons of Horus)|18th Company]]{{fn|2a}}*[[Kalus Ekaddon]] — [[Space Marine Captain|Captain]], [[Catulan Reaver Squad]]{{fn|2a}}*[[Falkus Kibre]] — [[Space Marine Captain|Captain]], [[Justaerin]] [[Terminator|Terminator Squad]]{{fn|2a}}*[[Nero Vipus]] — [[Space Marine Sergeant|Sergeant]], [[Locasta Tactical Squad]]{{fn|2a}}*[[Maloghurst]] — [[Equerry]] to the [[Warmaster]]{{fn|2a}}

*[[Nathaniel Garro]] — [[Death Guard#Combat Disposition and Record|Battle-Captain]] of the [[7th Company (Death Guard)|7th Company]]{{fn|2a}}

*[[Eidolon (Emperor's Children)|Eidolon]] — [[Lord Commander]]{{fn|2a}}*[[Saul Tarvitz]] — [[Space Marine Captain|First Captain]]{{fn|2a}}{{Fn|Conflicting sources}}*[[Lucius the Eternal|Lucius]] — [[Space Marine Captain|Captain]] of the [[13th Company (Emperor's Children)|13th Company]]{{fn|2a}}*[[Fabius Bile|Fabius]] — [[Emperor's Children]] [[Apothecary]]{{fn|2a}}

*[[Erebus]] — [[Chaplain|First Chaplain]]{{fn|2a}}

*[[Kharn the Betrayer|Kharn]] — [[Space Marine Captain|Captain]], [[8th Company (World Eaters)|8th Assault Company]], [[equerry]] to [[Angron]]{{fn|2a}}

*[[Esau Turnet]] — [[Princeps]] of the ''[[Dies Irae]]'', [[Legio Mortis]]{{fn|2a}}*[[Titus Cassar]] — [[Moderati Primus]] of the ''[[Dies Irae]]'', [[Legio Mortis]]{{fn|2a}}*[[Jonah Aruken]] — [[Moderati Primus]] of the ''[[Dies Irae]]'', [[Legio Mortis]]{{fn|2a}}

*[[Regulus (Dark Mechanicum)|Regulus]] — Representative to the [[63rd Expedition]]{{fn|2a}}

*[[Kyril Sindermann]] — [[Iterator|Primary Iterator]]{{fn|2a}}*[[Euphrati Keeler]] — [[Remembrancer|Offical Remembrancer]], Imagist{{fn|2a}}*[[Mersadie Oliton]] — [[Remembrancer|Offical Remembrancer]], Documentarist{{fn|2a}}*[[Peeter Egon Momus]] — Architect designate{{fn|2a}}*[[Maggard]] — Civilian enforcer{{fn|2a}}*[[Ing Mae Sing]] — Mistress of [[Astropaths]]{{fn|2a}}

*{{Endn|1}}: [https://www.blacklibrary.com/the-horus-heresy/novels/galaxy-in-flames-ebook.html Black Library] ''(last accessed 28th July 2022)*2: '''Galaxy in Flames''' (Novel):**{{endn|2a}}: ''Dramatis Personae''**{{endn|2b}}: ch. 1**{{endn|2c}}: ch. 2**{{endn|2d}}: ch. 3**{{endn|2e}}: ch. 4**{{endn|2f}}: ch. 5**{{endn|2g}}: ch. 6**{{endn|2h}}: ch. 7**{{endn|2i}}: ch. 8**{{endn|2j}}: ch. 9**{{endn|2k}}: ch. 10**{{endn|2l}}: ch. 11**{{endn|2m}}: ch. 12**{{endn|2n}}: ch. 13**{{endn|2o}}: ch. 14**{{endn|2p}}: ch. 15**{{endn|2q}}: ch. 16**{{endn|2r}}: ch. 17