Warhammer 40,000: The Two Lost Primarchs and Legions (II & XI)Fiction
In-universe lore. Claims are judged against the fiction's own canon, not the real world.
Two of the Emperor's twenty Primarchs - the masters of the IInd and XIth Space Marine Legions - were not killed by Chaos. They were deleted: names, faces and deeds scrubbed from every Imperial record by the Emperor's own decree, and it all happened before the Horus Heresy even began.
5 established, 3 disputed, 2 debunked, 3 unresolved. We do not pick an answer; the evidence places each claim. How we decide
45 citations from 16 independent sources - 29 echo the same voices and count once. Graded B1-D1.
Added 3 Jul 2026 - updated 6 Aug 2026 - canon current as of 6 Aug 2026
What the four states mean
- Establishedsupported, uncontested
- Disputedcredible sources disagree
- Debunkedrefuted by the evidence
- Unresolvedno settled answer
Established 5supported, uncontested
Of twenty Primarchs and Legions, two - the IInd and XIth - are blank in every Imperial roll, and the gap is deliberate, not an oversight.▰▰▰▱▱ likely4 points
Supports- Of twenty Primarchs and Legions, two - the IInd and XIth - are blank in every Imperial roll, and the gap is deliberate, not an oversight.A Thousand Sons (Black Library novel, 2010), Graham McNeill primary
- The Imperial Palace's Investiary held statues for all twenty Primarchs on ouslite plinths, but the 2nd and 11th stood permanently vacant, and no one ever spoke of the two absent brothers.The Two Missing Primarchs (lore essay on the Investiary in A Thousand Sons) analysis
- Guilliman, resurrected in Dark Imperium: 'I was one of twenty. Two failed. Half the rest turned on my father' - putting the count of Primarchs at exactly twenty.The Missing Primarchs - quoting Dark Imperium (Guy Haley) analysis
- Descent of Angels establishes the Lion as one of twenty brothers, confirming the full roster against which the IInd and XIth are missing.The Two Missing Primarchs - citing Descent of Angels (Mitchel Scanlon) analysis
Their erasure was a formal Edict of Obliteration - a Damnatio Memoriae - the most total scrubbing of records in Imperial history.▰▰▰▱▱ likely3 points
Supports- Their erasure was a formal Edict of Obliteration - a Damnatio Memoriae - the most total scrubbing of records in Imperial history.Imperial Armour Volume Nine - The Badab War, Part One (Forge World, Alan Bligh), which defines the Edict of Obliteration primary
- The deletion of all archive records of the IInd and XIth Legions is considered the most successful Edict of Obliteration ever carried out; Damnatio Memoriae is High Gothic for 'condemnation of memory.'Edict of Obliteration - Warhammer 40k Wiki summary
- The device was modelled on the Roman damnatio memoriae and on the legions annihilated at Teutoburg Forest, whose numbers Rome refused to ever reuse.YMMV / Horus Heresy - TV Tropes (real-world design origin) analysis
Whatever happened, it happened before the Heresy - the two were already gone and unspeakable when Horus turned traitor.▰▰▰▱▱ likely3 points
Supports- Whatever happened, it happened before the Heresy - the two were already gone and unspeakable when Horus turned traitor.The First Heretic (Black Library, Aaron Dembski-Bowden) primary
- Lorgar to Magnus: he fears the Emperor will break the Word Bearers, and that they would 'be cast alongside the brothers we no longer speak of' - the erasure already decades old by then.Lost Primarchs - Warhammer 40k Wiki (citing The First Heretic) summary
- In Prospero Burns, Leman Russ remarks that Astartes warring on Astartes is not unprecedented - implying the Space Wolves had been loosed on a Legion once before Prospero.Prospero Burns (Black Library, Dan Abnett) primary
The threat of erasure was a living weapon: Sanguinius hid the Blood Angels' flaw rather than risk becoming 'a third empty plinth.'▰▰▰▱▱ likely2 points
Supports- The threat of erasure was a living weapon: Sanguinius hid the Blood Angels' flaw rather than risk becoming 'a third empty plinth.'Fear to Tread (Black Library, James Swallow) primary
- Sanguinius refuses to confess the Red Thirst: he will not be responsible for the Blood Angels' erasure, nor have 'a third empty plinth beneath the roof of the Hegemon' as his Legion's only memorial.YMMV / Horus Heresy - TV Tropes (quoting Fear to Tread) analysis
The lost Legions' gene-seed still exists in the 42nd Millennium: Belisarius Cawl holds it - and Guilliman forbade him to use it.▰▰▰▱▱ likely2 points
Supports- The lost Legions' gene-seed still exists in the 42nd Millennium: Belisarius Cawl holds it - and Guilliman forbade him to use it.Belisarius Cawl: The Great Work (Black Library, Guy Haley, 2019) primary
- Cawl reveals he has extracted the gene-seed of the IInd and XIth from the Sangprimus Portum and wants to found new chapters from it; Guilliman vehemently refuses and orders the research halted.Two unknown legions - Lexicanum (citing Belisarius Cawl: The Great Work) summary
Disputed 3credible sources disagree
The strongest in-canon suspect for the purge is the Space Wolves, the Emperor's Executioners - but the authors refuse to confirm it.▰▰▰▱▱ likely1 against4 points
Supports- The strongest in-canon suspect for the purge is the Space Wolves, the Emperor's Executioners - but the authors refuse to confirm it.Prospero Burns (Black Library, Dan Abnett) primary
- Asked whether he worried about Astartes fighting Astartes for the first time, Russ answers that it is not unprecedented - read as the Wolves having censured a Legion once before.Warhammer 40k lore: What happened to the lost legions? - Wargamer (citing Prospero Burns) analysis
- The Space Wolves are canonically styled the Emperor's Executioners and sanction Legion - the obvious instrument for a Legion-on-Legion purge.Space Wolves - Lexicanum summary
Against- Aaron Dembski-Bowden, asked directly if the Wolves destroyed the lost Legions, declined: that would be an answer, and there is not allowed to be an answer.Wargamer - paraphrasing ADB's 2018 reddit comment on the lost legions analysis
Treason, tragedy, or simple failure? Canon's own hints about the lost Primarchs' crime openly contradict each other.▰▰▰▱▱ likely1 against4 points
Supports- Treason, tragedy, or simple failure? Canon's own hints about the lost Primarchs' crime openly contradict each other.The Missing Primarchs - survey of the contradictory canon hints analysis
- Failure reading: Guilliman in Dark Imperium says 'Two failed' and separates them from the brothers who 'turned' - inadequacy, not betrayal.The Missing Primarchs - quoting Dark Imperium (Guy Haley) analysis
- Tragedy reading: in Deliverance Lost, Corax asks the Emperor about his missing brothers; the Emperor's face grows bleak and he answers 'The other two... a conversation for another day' - grief, not condemnation.Deliverance Lost (Novel) - Lexicanum (Gav Thorpe) summary
Against- Crime reading: the lost are spoken of with dread even by Primarchs who would themselves become traitors, implying a transgression so vast that betrayers will not name it.The Two Missing Primarchs (on The First Heretic and the tone of dread) analysis
A popular theory holds the survivors were folded into the Ultramarines - which mysteriously ballooned at the very same time.▰▰▰▱▱ unlikely2 against4 points
Supports- A popular theory holds the survivors were folded into the Ultramarines - which mysteriously ballooned at the very same time.Lost Primarchs - Warhammer 40k Wiki (Ultramarines absorption theory) summary
- Around the time the IInd and XIth were expunged, the XIIIth (Ultramarines) swelled in numbers to eclipse every other Legion - the circumstantial basis for the absorption theory.Lost Primarchs - Warhammer 40k Wiki summary
Against- Against it: in M42 Cawl still holds separately-catalogued IInd and XIth gene-seed in the Sangprimus Portum, implying the lines were preserved apart rather than simply absorbed into the XIIIth.Belisarius Cawl: The Great Work (Guy Haley) primary
- Readers themselves raise the 'Ultramarines picked up the leftovers' idea to Dembski-Bowden as open speculation; no canon source confirms it.Questions and Answers - Aaron Dembski-Bowden blog (reader question 91) analysis
Debunked 2refuted by the evidence
Debunked: the lost two were NOT traitor Legions who fell to Chaos like the other nine.Refuted by
The common fan assumption is Chaos, because betrayal defines the Heresy - but the pre-Heresy timing of the purge rules that out.
refuted1 against4 pointsThe claim rested on- Debunked: the lost two were NOT traitor Legions who fell to Chaos like the other nine.The Missing Primarchs - quoting Dark Imperium (Guy Haley) analysis
- Guilliman: 'I was one of twenty. Two failed. Half the rest turned on my father' - the two who 'failed' are explicitly distinct from the half who turned traitor.The Missing Primarchs - quoting Dark Imperium analysis
- The nine traitor Legions kept their names, numbers and records; only the IInd and XIth were obliterated - and their erasure predates Horus's rebellion by decades.Lost Primarchs - Warhammer 40k Wiki summary
Refuted by- The common fan assumption is Chaos, because betrayal defines the Heresy - but the pre-Heresy timing of the purge rules that out.Warhammer 40k lore: What happened to the lost legions? - Wargamer analysis
Debunked: there is no secret 'official answer' being saved up for a future big reveal.Refuted by
Fans persistently expect a novel or codex to finally name them; the lore is argued to be built precisely to invite that hope while never paying it off.
refuted1 against4 pointsThe claim rested on- Debunked: there is no secret 'official answer' being saved up for a future big reveal.Warhammer 40k lore - Wargamer (on ADB's refusal to answer) analysis
- Dembski-Bowden on whether the Wolves did it: that would be an answer, and there is not allowed to be an answer - i.e. there is nothing being withheld for later.Warhammer 40k lore: What happened to the lost legions? - Wargamer analysis
- Rick Priestley says he left the Legions blank to pose 'questions for which there could be no answer' - by design there is nothing to reveal.Lore and mystery in 40k - Death by D6 (quoting Priestley) analysis
Refuted by- Fans persistently expect a novel or codex to finally name them; the lore is argued to be built precisely to invite that hope while never paying it off.What happened to the Lost Primarchs? Invitational incompleteness - Warhammer Conference (Nathan Wildman) analysis
Unresolved 3no settled answer
Their names, faces and fates have never been revealed - and the void is by design, an invitation for fans to fill.▰▰▰▱▱ likely4 points
Supports- Their names, faces and fates have never been revealed - and the void is by design, an invitation for fans to fill.What happened to the Lost Primarchs? 'Invitational incompleteness' - Warhammer Conference (Nathan Wildman) analysis
- Wildman argues the lost Primarchs are a deliberate 'invitational incompleteness' - a gap left open to entice readers to fill it with their own explanations and stories.Invitational incompleteness - Warhammer Conference analysis
- Priestley notes he detailed only about a dozen of a thousand Chapters, leaving the rest 'blank for people to fill in' - the same design instinct behind the two Legions.New Lost Legions background by Rick Priestley - Bolter and Chainsword analysis
- Asked if he would write the IInd or XIth, the question itself jokes it would start 'a massive Black Library author bar room brawl' - the blanks are intentionally unowned by any single writer.Questions and Answers - Aaron Dembski-Bowden blog (reader question 91) analysis
The only 'facts' that leaked: a stray record puts II & XI at the Rangdan Xenocides, and a Forge World book literally prints '[REDACTED]'.▰▰▰▱▱ likely3 points
Supports- The only 'facts' that leaked: a stray record puts II & XI at the Rangdan Xenocides, and a Forge World book literally prints '[REDACTED]'.The Horus Heresy Book Seven: Inferno (Forge World, Alan Bligh) primary
- Inferno's account of the Rangdan Xenocides states that entire Space Marine Legions were [REDACTED] lost to the Imperium - the redaction printed verbatim in the official text.Rangdan Xenocides - Lexicanum (citing HH Book Seven: Inferno) summary
- A record reportedly bound by accident into copies of the Imperial Infantryman's Uplifting Primer names the IInd and XIth among forces in the Rangdan Xenocides in the 860s.M30, scope 'unrecorded.'Rangdan Xenocides - Warhammer 40k Wiki summary
The man who invented the gap, co-creator Rick Priestley, says it was meant to be unknowable - and that the Horus Heresy series 'ruined' it.▰▰▰▱▱ likely4 points
Supports- The man who invented the gap, co-creator Rick Priestley, says it was meant to be unknowable - and that the Horus Heresy series 'ruined' it.Lore and mystery in 40k - Death by D6 (quoting Rick Priestley's 2018 r/40kLore interview) analysis
- Priestley: he left the Legions blank to give the story 'unknowable ten thousand year old mysteries - stuff that begs questions for which there could be no answer.'Lore and mystery in 40k - Death by D6 analysis
- Priestley: 'all that got ruined when some bright spark decided to use the Heresy setting - which rather spoiled the unknowable side of things.'New Lost Legions background by Rick Priestley - Bolter and Chainsword analysis
- He adds the Heresy as published 'just feels like 40K - it doesn't have the feel of a genuinely different society that ten thousand years separation would give you.'New Lost Legions background by Rick Priestley - Bolter and Chainsword analysis
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