Honsou, a champion of another Warsmith at the time controlled one of the three segments of "The Warsmith"'s Grand Company. He was looked down upon by his fellow marines, due to the fact that his gene-seed was a meld of that of the Iron Warriors, and that of the Imperial Fists. He was often referred to as "Half-Breed". Honsou's gene-seed originated from 'Honourable' Soulaka, an Iron Warriors Apothecary who was murdered by Fabius Bile, who was then responsible for melding Soulaka's gene-seed with that of an Imperial Fist, likely Captain Felix Cassander. It is highly possible that Honsou's name originated from the container that Soulaka's gene-seed was kept in, as after a laboratory accident part of the name had been wiped off leaving only "Hon Sou".
He took part in the besieging of the Adeptus Mechanicus fortress of Hydra Cordatus alongside his chief rivals Forrix and Kroeger, all under the command of "The Warsmith". The fortress was known to house large amounts of gene-seed belonging to the Imperial Fists Space Marine chapter, the sworn enemies of the Iron Warriors. The siege was successful elevating the existing Warsmith to Daemonhood and with both Honsou's chief rivals dead he was promoted to Warsmith by the Daemon prince. He then returned to Medrengard with the gene-seed captured from the fortress.
Return to Medrengard
Though he claimed that the gene-seed was sent to the Despoiler, Honsou kept some for himself. Using the captured gene-seed, Honsou constructed an unusual manufacturing system, the Daemonculaba, which allowed him to create new Iron Warrior space marines. However, the Daemonculaba was far from perfect, and many of the candidates were flushed out. Many did not survive, and those that did were horribly mutated beasts called the Unfleshed, and were cast out from Honsou's fortress.
Honsou then led his warriors into a civil war with two rival Warsmiths, Lord Toramino and Lord Berossus, as he refused to uphold his predecessor's promise to share the stolen gene-seed amongst the Iron Warrior commanders. During the war, the exiled Ultramarines captain, Uriel Ventris led a group of renegade space marines to infiltrate Honsou's fortress in a misson to destroy the Daemonculabu. They were captured and brought before Honsou who thought they were mercenaries acting on behalf of Toramino; he also took an interest in Pasanius' living metal bionic arm (who was also exiled along with Ventris and bound by a Death Oath). Afterwards they were sent to be tortured by the Savage Morticians, and Pasanius' arm was cut off for Honsou to wear. He later became enraged with the Savage Morticians, as Ventris escaped along with a few survivors.
Lord Berossus made one final push to which he managed to successfully storm Khalan Ghol and duel Honsou. However, Honsou defeated Berossus with the support of his Daemonhost bodyguard Onyx. After Berossus' death, his men defected over to Honsou's side after he swayed them to join him in fighting against Toramino. During this battle, Venris had infiltrated Honsou's fortress once again, but this time leading a band of the Unfleshed. Ventris destroyed the Daemonculabu and set free the Heart of Blood, a powerful Daemon captured by the Iron Warriors which had acted as a psychic barrier against enemy sorcerers. When the daemon was set free, the psychic defences fell down, allowing Toramino's forces to attack the fortress with psychic attacks. Honsou returned into his fortress and cornered Ventris and Pasanius before they made their escape. Before Honsou's retinue had a chance to kill the Ultramarines, the Unfleshed arrived to attack and kill Iron Warriors. Ventris also shot down Honsou in the head who was fleeing from the battle.
After the Ultramarines left, Honsou was found to have survived. He then discovered the Heart of Blood collapsed on the floor after exhaustion from winning its earlier battle with its rival daemon, the Omphalos Daemonium. Honsou went on to direct the Heart of Blood against his rival Toramino's army. Given the extent of the daemon's power, this would have undoubtedly won the war for Honsou. Despite the loss of the Daemonculaba and many of his men, Honsou consolidated his power, and began rebuilding his army. His last known action on Medrengard was to invite the remaining renegades who survived, including Cadaras Grendel and Ardaric Vaanes, into his army, and it was also revealed that within his new retinue was the Newborn, a clone of Uriel Ventris, earlier created by the Daemonculabu before it had been destroyed. 
Though Honsou had triumphed over Warsmiths Berossus and Toramino, he had also suffered defeat at the hands of Uriel Ventris. Soon thereafter, he departed Medrengard on a mission of vengeance. Honsou and his retinue arrived at a space station orbiting Tarsis Ultra. They quickly slaughtered the space station's crew, and then commandeered multiple orbital torpedoes. Honsou infused an experimental genetic growth strain, known as the Heraclitus strain, into the warheads of the torpedoes and launched them against Tarsis Ultra. The torpedoes detonated in the planet's atmosphere, sending the Heraclitus strain across the planet's surface. Tarsis Ultra had recently repelled an invasion by Tyranids thanks to Uriel Ventris and the Ultramarines. However, the Tyranids left some plant spores behind. As intended, the Heraclitus strain interacted with the Tyranid spores, causing the plantlife to rapidly grow and spread at a rate of several square kilometers per minute. This caused a chain reaction which, ultimately, caused billions of citizens of Tarsis Ultra to perish, and rendered the planet itself a cold, lifeless rock. All this was done to spite Ventris and issue the galaxy a warning: nobody trifles with Honsou without paying an extremely dear price. 
The Skull Harvest
Honsou travels to the Maelstrom in search of recruits. He plans to lead a mighty army to Ultramar, razing it to the ground, and the skull harvest seems to be an ideal way to raise an army. The Skull harvest is an annual event, hosted by Huron Blackheart which entails mighty warlords bring their warbands to the planet of New Badab. Honsou arrives just prior to the start of one. He sets up a camp with his fellow Iron Warriors, and participates in the event with the main, underlying rule being that whoever slays the leader of a warband may claim the warband for their own. Honsou sends The Newborn (Uriel Ventris' clone) and an ex-member of the Raven Guard to fight the other warlords champion. They both do well, and swell Honsou's army to the size of 5,000. Eventually Honsou, a Khornate champion named Pashtoq, and a Slanneshi champion named Noshta are the only members left. Pashtoq upholds a large dislike of Honsou, mainly because Honsou killed one of his mighty champions with the help of his bionic arm, and the fact that Honsou is a half-breed. Noshta is swiftly defeated, and Honsou is left fighting Pashtoq. He destroys Pashtoq's Daemon Weapon with his own, but Pashtoq calls for one of his champions to bring him a new one. In response, the champion (who has allegiances with Honsou) plunges the new weapon into Pashtoq's chest. Honsou then cuts off his head, winning the Skull Harvest. A wounded Noshta swears his allegiance to him, and Honsou leaves New Badab with a force of almost 17,000 warriors. But before he leaves, Huron Blackheart warns him, telling him to kill his champions as soon as they become un-useful, to prevent a possible mutiny. His final words to Honsou before he leaves New Badab are "Always remember. The strongest are Strongest alone".
War for Ultramar
Using Morianna, the damned seer of the Despoiler, Honsou was able to free the Daemon Prince M'kar, an ancient enemy of the Ultramarines who had been imprisoned on the Indomitable space fort by Chapter Master Marneus Augustus Calgar. With his army ready, Honsou unleashed his plan for revenge against Uriel Ventris: the complete destruction of Ultramar. Striking first at Tarentus, Honsou had M'kar unleash his daemon army on the planet's domed city, destroying all it's inhabitants. It was only after this that Honsou realized that M'kar had forced himself into a position of sharing with Honsou command of the army (which the daemon dubbed the Bloodborn), a situation neither could tolerate for long.
Honsou later took Grendel, Vaanes, and the Newborn to Calth, Ventris's homeworld, with instructions from M'kar to destroy the Tomb of Ventanus, a famed Ultramarines captain who defended the planet from the Word Bearers during the Horus Heresy, as M'kar himself was unable to go near Calth. Before being accepted into the Ultramarines, a young Ventris had discovered the tomb in his youth, it's location was something the Newborn knew. Vaanes was captured in the initial battle for Guilliman's Gate, but Honsou, Grendel, and the Newborn were able to find the tomb. As they prepared to destroy the tomb, Honsou investigated Ventanus's sarcophagus, finding the Shard of Erebus, a combat knife buried with the captain. Honsou surmised that due to M'kar's fear of Calth and Venatus's wargear, the knife was capable of harming the Daemon Prince. When Ventris arrived with his squads and a group of Raven Guard, Grendel and the Blade dancers were killed initially. Honsou then charged the Newborn with killing Ventris, but Ventris was able to defeat his clone. A battle erupted, during which Honsou mortally wounded Vaanes, but the Iron Warriors were in turn defeated by what appeared to be the ghost of Remus Ventanus and the Legion of the Damned. With his Iron Warriors dead, Honsou activated the trigger for the bombs intended to destroy the tomb, burying Ventris and his allies. Although Ventris, Pausanius, and most of the Astartes present survived the explosion, Honsou's body was never found. Additionally, the drilling machine that had carried the Iron Warriors to the tomb also disappeared, indicating that Honsou may have escaped.
- "That's what you don't understand about me, Vaanes. I don't care. I do what I want because it is who I am. Anything else is a lie and if there is one thing I can say of myself, it is that I will never compromise who I am. Not for the powers of the warp, not for the M'kar and certainly not for you. When death is a heartbeat away, I am truly alive. That's the only way I know how to live. What else is there?"[6a]
- "Beyond that opening are my enemies. Behind me are warriors who would happily turn their weapons on me if they thought they could get away with it. Do you really think I'm doing this to try and impress anyone? I know who I am, and I don't give a greenskin's fart what anyone thinks of me."
- "Honsou paid scant regard for any doctrinal approach to warfare, fighting from the hip and with a frighteningly intuitive grasp of the nature of any combat. His situational awareness of the shape of a battle was unmatched, and he could read its ebbs and flows better than anyone Uriel had met. To know when to consolidate, to advance, to flank and when to gamble; these were the qualities most leaders of men had to learn in the bitter fires of bloodshed but which Honsou possessed innately." - Uriel Ventris on Honsou
- 1: Storm Of Iron (Novel) by Graham McNeill
- 2: Dead Sky, Black Sun (Novel) by Graham McNeill
- 3: The Skull Harvest (Short Story) by Graham McNeill
- 4: The Heraclitus Effect (Short Story) by Graham McNeill
- 5: Iron Warrior (Novella) by Graham McNeill
- 6: The Chapter's Due (Novel) by Graham McNeill
- 6a: Chapter Nine, pgs. 120-121
- 7: The Iron Without (Short Story) by Graham McNeill
- 8: The Beast of Calth (Short Story) by Graham McNeill
- 9: Angel Exterminatus (Novel) by Graham McNeill, Epilogue 'Theogenies IV'.