The Avenging Sons hail from the world of Traekonnis Major.
The Avenging Sons were raised during the 19th Founding in the mid-36th Millennium.
They are a Successor Chapter of the Ultramarines and proudly maintain that Chapter's vaunted martial traditions and their stoic faith in the tenets of the Codex Astartes written by their Primarch, Roboute Guilliman.
- Space Port on Archimedon (Unknown Date.M41) - The world of Archimedon was the place where a major engagement of the Avenging Sons' 3rd Company unfolded. Their mission was to defend a spaceport on the planet. However, after the battle turned against them, they destroyed the spaceport themselves rather than let it fall into enemy hands. The Chapter Master of the time disagreed with this course of action, but he did not formally punish the company. The 3rd Company suffered substantial losses in this battle, including their Chaplain (who was replaced afterwards by Chaplain Herdain) and these losses helped to prime the company for the betrayal of the Emperor they would carry out on the world of Helmabad.
- Helmabad Rebellion (970.M41) - The Avenging Sons' Captain Gessart and his 3rd Company turned Renegade whilst fighting in the civil war on Helmabad against a force of Chaos Cultists, who had stirred up a rebellion against the Emperor, to save their own lives when the course of the battle went against them. Killing their Chaplain and those Loyalist battle-brothers who would not follow them, the Space Marines of the 3rd Company negotiated with the Traitors for safe passage to their Thunderhawk in return for leaving the Planetary Governor undefended for the cultists to slay. After fleeing the planet, which had been struck by a Warp Storm, the 3rd Company painted over their Chapter badges and other Imperial symbols and set course for the Eye of Terror. It should be noted that Captain Gessart intended to continue fighting for the good of humanity, yet could not remain as part of the Avenging Sons Chapter after he had allowed the elimination of those Space Marines who had refused to abandon the world of Helmabad to Chaos to save their own lives. This event has left a nigh indelible stain on the Chapter's honour. The renegade Astartes of 3rd Company have been sighted on at least three separate occasions between 996.M41 and 998.M41 in the vicinity of the Cadian Gate, each sighting moving ever closer to the Eye of Terror.
- Liberation of Antillis IV (Unknown Date.M41) - The Avenging Sons' 2nd Company led by Force Commander Selleus took extremely heavy casualties during the Antillis IV campaign to recover that world from the forces of Chaos. Outnumbered by a Chaos force led by a warband of Chaos Space Marines of the Black Legion, the detachment was ground down and eventually surrounded. Their defences broken, they fought to the end, detonating their position just at the moment of being completely overrun. The only known survivor was a single member of an attached Scout Squad and a Thunderhawk gunship which contained a large portion of the company's precious gene-seed, extracted during the battle.
- Taros Campaign - First Taros Intervention (998.M41) - A strike force composed of the Avenging Sons' 2nd Company fought in the first Imperial intervention that began the Taros Campaign on the desert Mining World of Taros in the Ultima Segmentum. The Avenging Sons' Captain Armaros led a Kill-team comprising a single reinforced company of the Avenging Sons to Taros in order to execute Planetary Governor Uphir Aulis within the Governor's Palace for his traitorous dealings with the T'au Empire, but the Space Marines were surprised by Taronian Planetary Defence Forces and a large contingent of T'au Fire Warriors who were secretly on the world to try and seize it from the Imperium. As a result of the unexpectedly large presence of the T'au Fire Caste on Taros, the Avenging Sons' mission failed and they had to extract themselves from the world with heavy casualties, including the loss of a Dreadnought.
Notable Avenging Sons
- Captain Armaros - Amaros was the Avenging Sons Kill-team Force Commander during the First Taros Intervention of the Taros Campaign as well as captain of the 2nd Company.
- Captain Gessart - Disgraced for dishonourably withdrawing his forces during the Archimedon Campaign, Captain Gessart and the Avenging Sons' 3rd Company were reassigned to fight a grueling campaign on the world of Helmabad. Feeling the strain of continuous warfare and angered by the unprofessional standards of the Helmabad Planetary Defence Force, Gessart became disillusioned. He soon learned from the company's Librarian that Helmabad was mere hours away from a massive incoming daemonic assault, and that to stand and defend it would mean certain death. Desperate to survive what he saw as a pointless sacrifice, Gessart resolved to withdraw his forces from the doomed planet. When his proposed plan was met with open hostility by Chaplain Herdain, the desperate Gessart murdered the Chaplain in cold blood. He then removed any further resistance within his company until only battle-brothers loyal to him remained. Gessart ordered his company to subjugate the Helmabad PDF and secure the Imperial Governor as a hostage. He turned the Governor over to the rebel Chaos Cult forces as a bargaining chip in order to secure passage off-world. Unable to reconcile these dishonourable actions with his Chapter, Captain Gessart soon realised that he and his men had become Renegades and ordered his company to chart a course for the Eye of Terror.
- Force Commander Selleus - Selleus was the force commander who led the Avenging Sons' 2ndCompany during the Liberation of Antillis IV.
- Chaplain Herdain - A resolute and staunch battle-brother, Chaplain Herdain was reassigned to the 3rd Company after their dishonourable actions during the Archimedon Campaign, and resolved that he would ensure that the company's Astartes were absolved of their sins by achieving a noble death during the grueling campaign on Helmabad. When Captain Gessart informed the Chaplain of the approaching daemonic incursion and made the suggestion that they should withdraw, the Chaplain refused to countenance such cowardice and was provoked into confronting the disreputable captain for command of the company. When he attempted to sway the men of the 3rd Company to support him, Gessart ended the debate by shooting Herdain in the head, killing him instantly.
- Chaplain Baraqel - An Avenging Sons Chaplain who participated in the First Taros Intervention.
- Epistolary Gathein - Gathein was a Primaris Space Marine and a member of Tetrarch Decimus Felix's Honour Guard called the Chosen of Vespator.
- Librarian Zacherys - Zacherys was the Librarian assigned to the 3rd Company. His prophetic visions helped influence the company's actions. When he informed Captain Gessart of the impending daemonic incursion that would arrive in a matter of hours as part of a Warp Storm that would engulf the doomed world of Helmabad, Gessart resolved to withdraw his forces and save his men by any means possible. Zacherys stood by his captain and supported his decision after discerning the meanings of his visions; for he knew that to stay on the planet meant certain death.
- Apothecary Tylo - Tylo was an Apothecary assigned to the 3rd Company. He sided with Captain Gessart against Chaplain Herdain, claiming that to allow their Chapter's gene-seed to fall into the hands of the forces of Chaos was unthinkable.
- Apothecary Korpus - 2nd Company Apothecary during the Antillis IV Campaign.
- Apothecary Actium - Actium participated in the First Taros Intervention.
- Veteran Sergeant Einem - Einem took part in the First Taros Intervention.
- Sergeant Andura (KIA) - Andura took part in the First Taros Intervention as the leader of 3rd Tactical Squad. He was killed by the T'au during the first phase of the operation.
- Veteran Sergeant Foras - Foras was a Veteran sergeant of the 1st Company who took part in the First Taros Intervention.
- Hechsen - Hechsen was a battle-brother of the 3rd Company who sided with Chaplain Herdain, choosing execution at the hands of his fellow battle-brother, Nicz, rather than sully his company's honour further by withdrawing from Helmabad in disgrace.
- Karlrech - Brother Karlrech was a battle-brother of the 3rd Company who sided with Chaplain Herdain's decision to stay and die an honourable death, refusing to change his mind even after Herdain's execution, and was subsequently executed at the hands of Brother Nicz.
- Lehenhart- Lehenhart was a battle-brother of the 3rd Company who sided with Captain Gessart's decision to withdraw, declaring that to do so was not cowardice, but survival. To fight against impossible odds was tantamount to committing suicide.
- Nicz - Nicz was a battle-brother of the 3rd Company who sided with his commander's decision to withdraw from the doomed world of Helmabad, though his viewpoint was more extreme than even Gessarts' own; the situation was untenable and the company's honour meant nothing compared to survival. In the end, after the 3rd Company's Astartes successfully carried out their plan and withdrew from the doomed world, Gessart realised that they had truly become Renegades and ordered the company to set course for the Eye of Terror. Realising his folly, Nicz attempted to assert his authority over his commander, but the captain confronts Nicz and dared his subordinate to shoot him if he believed that he could best him. Nicz relented and stood down, resigned to his fate as a Traitor to the Emperor.
- Ruphen - Ruphen was a battle-brother of the 3rd Company who agreed with Chaplain Heldain's decision to stay on Helmabad and die honourably. He was the first Avenging Son to draw his weapon and aim it at a fellow battle-brother.
- Rykhel - Rykhel was a battle-brother of the 3rd Company who also agreed with Chaplain Heldain's decision, declaring his oaths of loyalty to the Chapter meant that he had no say as to the manner or place of his death. Reluctantly, he went along with Captain Gessart's devious plan after Heldain was executed. After the 3rd Company successfully withdrew from the planet, Rykhel elected to desert in an escape pod to bring word to his Chapter of Gessart's treachery. Considering the only place he would be able to land safely was controlled by Heretics and was about to be overrun by a daemonic incursion unleashed by an onrushing Warp Storm, Gessart doubted that Rykhel would live long enough to carry out his plan.
- Willusch - Willusch was a battle-brother of the 3rd Company who sided with Captain Gessart; to throw the 3rd Company's lives away in such a pointless manner was a needless self-sacrifice.
- Heynke - Heynke was a battle-brother of the 3rd Company who was unsure which side to choose, but eventually chose to support the opinion of the vast majority of the 3rd Company, and agreed to Captain Gessart's plan to withdraw their forces from Helmabad.
- Chaim (Dreadnought) - Brother Chaim was a Mark V Dreadnought of the Avenging Sons' 2nd Company who served during the First Taros Intervention of the Taros Campaign. He was killed in action against the Tau during the failed attempt to assassinate the heretical Planetary Governor of Taros, Uphir Aulis.
- Hakael (Dreadnought) - Brother Hakael was a Mark IV Dreadnought of the Avenging Sons' 2nd Company who served during the First Taros Intervention of the Taros Campaign Kill-team.
The Avenging Sons have an average-sized Chapter Fleet, of which the only known vessels are:
- Proxima Justus (Strike Cruiser) - The Proxima Justus delivered the Avenging Sons' 2nd Company to the desert Mining World of Taros during the First Taros Intervention in the unsuccessful attempt to assassinate the Planetary Governor Uphir Aulis that set off the Imperial Taros Campaign against the Tau in 998.M41.
- Vengeful (Strike Cruiser) - The Vengeful belonged to the former commander of the 3rd Company, Captain Gessart. When the commander fled the doomed planet of Helmabad in the face of an impending daemonic incursion and Warp Storm, Gessart ordered the vessel to make course for the Eye of Terror, as they were now true Renegades and would never be able to reconcile with their Chapter.
A black High Gothic numeral is stenciled on the centre of the squad specialty symbol which indicates squad number.
The colour of the shoulder pauldron trim indicates company number in accordance with the dictates of the Codex Astartes, i.e. White (1st Company), Yellow (2nd Company), Red (3rd Company), Green (4th Company), etc.
The Avenging Sons' Chapter badge is a white crosslet, centred on a field of azure.
In the novel Dark Imperium by Guy Haley, a Chapter of Primaris Space Marines is raised at the Pit of Raukos as the last action of the Ultima Founding, and it is called the Avenging Sons. Roboute Guilliman based this new Chapter at the world of Callimachus within the growing Realm of Ultramar.
It is not known whether the name of this Primaris Marine Chapter is a mistake or if it has some connection to the original Avenging Sons.
- Adeptus Astartes: Successor Chapters (Limited Release Booklet), pg. 15
- Imperial Armour Volume Two - Second Edition: War Machines of the Adeptus Astartes, pp. 8-9
- Imperial Armour Volume Three - Taros Campaign, pp. 19, 22-35
- Imperial Armour Volume Thirteen - War Machines of the Lost & The Damned, pg. 33
- Insignium Astartes, pg. 60
- Dark Imperium (Anthology) (2001), "Apothecary's Honour" by Simon Jowett
- Heroes of the Space Marines (Anthology) edited by Nick Kyme and Lindsey Priestley, "Renegades" by Gav Thorpe, pg. 79
- Dark Imperium (Novel) by Guy Haley, Ch. 20
- The Rewards of Tolerance (Short Story) by Gav Thorpe
- Belisarius Cawl: The Great Work (Novel) by Guy Haley, Ch. 5