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What is Warhammer 40k Arks of Omen?

A guide to Games Workshop’s Arks of Omen narrative, the biggest story event of Warhammer 40k 9th Edition, including the return of Lion El Jonson.

Warhammer 40k Arks of Omen - Games Workshop image showing Abaddon the Despoiler with his Black Legion marines

Warhammer 40k Arks of Omen is a book series, released by Games Workshop in 2023 to advance the evolving narrative of Warhammer 40k. Bringing 9th Edition to a close, it introduced fresh plot developments, new main characters, and a new game mode for battles on board spaceships – plus the return of a second Space Marine primarch. If you’re coming back in for 10th Edition, this is essential lore background – read on for the full details.

GW released five Arks of Omen books over the course of 2023, in the process introducing new daemonic main character Vashtorr the Arkifane; advancing the overarching story of the Warhammer 40k Chaos forces as they plunge the galaxy into a new era of war; and culminating with the surprise return of Dark Angels primarch Lion El Jonson to the Warhammer 40k universe.

Warhammer 40k Arks of Omen - Games Workshop image showing an artwork of Vashtorr the Arkifane

The series delivered 2023’s biggest events for all the Warhammer 40k factions, and laid the foundations for Warhammer 40k 10th edition. Here’s what you need to know.

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Arks of Omen models

When GW first announced Arks of Omen, it said that a key design goal was to prevent players from having to use more than one book – that means there will be no new Arks of Omen models. But each book will have a strong theme, and some new special characters are confirmed to be releasing alongside the books.

They weren’t kidding, either. First we got Vashtorr the Arkifane himself, facing off against a brand new Primaris Azrael of the Dark Angels in the Wrath of the Soul Forge King boxset, released in March 2023. Then, in April, just as GW was pulling back the curtain on the incoming new 10th Edition of 40k, it released the brand new Lion El Jonson model too – putting a cap on the Arks of Omen storyline and looking ahead to a new 10th Edition narrative with a distinctly more Tyranid flavouring.

What are the Arks of Omen?

In essence, the Arks of Omen are the latest ploy for galactic conquest by everyone’s favourite Chaos warmaster. No, not Horus Lupercal – we’re talking about Abaddon the Despoiler. After splitting the galaxy in half with the Cicatrix Maledictum and blowing up Cadia in the 13th Black Crusade, Abaddon has discovered a bit of a problem on his hands.

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He’s trying to overrun the galaxy, but there’s only so much he, the Black Legion, and his allies can achieve – especially when you’re trying to take on the Imperium of Man without relying on the Chaos Gods too much. After all, he saw what happened back in the 31st millennium with the Horus Heresy, and has vowed never to let the machinations of Khorne, Slaanesh, Nurgle, or Tzeentch get too much of a hold over him or his forces.

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Enter Vashtorr the Arkifane. Unaligned with any of the four Chaos Gods, this malevolent warp entity has allied itself with Abaddon, sharing its knowledge of combining daemon-flesh with technology to help construct the Arks of Omen.

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At the heart of each ark is a colossal space hulk wreck, twisted and enhanced with dark magics and daemonic weaponry to create devastating battleships. Around each Ark of Omen, an armada of heretic vessels has been assembled, forming vast Balefleets that can wreak untold destruction on Abaddon’s foes.

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Abaddon has awarded Arks of Omen to select Chaos warbands, deployed across the galaxy to hunt down and retrieve arcane artefacts of mysterious purpose. Bristling with furious intent and filled with swarms of the warmaster’s loyalists, these mobile space fortresses may be the tipping point he needs to turn the long war in his favour once and for all. The Arks of Omen are coming, and nowhere looks to be safe from Abaddon’s long reach.

Warhammer 40k Arks of Omen - Games Workshop image showing a graphic for the Arks of Omen books' release schedule

Arks of Omen books

Games Workshop released five Arks of Omen books, each focusing on a particular character as part of the overarching narrative. The four books were:

Title Release date
Arks of Omen: Abaddon January 14, 2023
Arks of Omen: Angron February 11, 2023
Arks of Omen: Vashtorr March 18, 2023
Arks of Omen: Farsight April 1, 2023
Arks of Omen: The Lion April 22, 2023

Warhammer 40k Arks of Omen - Games Workshop image showing Chaos Space Marines in battle

Arks of Omen plot summary

The Arks of Omen plot involves Abaddon and Vashtorr using said Arks to search far and wide for various dark artefacts known as fragments of ‘The Key to the Lock’, which, once united, will unlock ‘The Weapon’. We don’t know what The Weapon is, but Abaddon believes it has the power to destroy the Imperium of Man, so naturally he wants it.

Through various winding story segments, we follow Abaddon and Vashtorr’s hunt for the key fragments, and the assorted forces opposing them – including not only Imperials but xenos races too, most notably the Tau Empire‘s Commander Farsight.

At the story’s climax, the gruesome twosome spring a huge trap on the Dark Angels in order to assault their flying fortress monastery, The Rock, and claim the final piece of the Key: an ancient technological device called the Tuchulcha Engine, which the Dark Angels had been hiding deep inside The Rock since the Horus Heresy.

Luring the Dark Angels and other Imperial allies to the Somnium Stars, they present the loyalists, on arrival, with a grotesque surprise: a realistic, life-size, warp-twisted replica of the Dark Angels’ long since destroyed home planet, Caliban.

Despite knowing they’re walking into a trap, the honor-bound knightly warriors of the Dark Angels deploy to the planet – lovingly named ‘Wyrmwood’ by Vashtorr – and launch a vengeful war against the armies of Chaos Space Marines and Chaos Daemons on the surface.

In the process, reinforcements from the Blood Angels arrive, and with them – to the astonishment of every Dark Angel – comes the newly returned primarch Lion El’Jonson, in all his wrathful glory. The Lion joins the fight on Wyrmwood and leads the Imperials to victory, along the way having an epic duel with his daemonic brother Angron, primarch of the World Eaters.

Reorganising their forces, routing their chaotic enemies under the Lion’s leadership, and evacuating, the Imperial fleet successfully blows the planet Wyrmwood to bits from orbit, along with any chaos forces still on it – but at great cost in Space Marine lives.

And, worst of all, Vashtorr’s distraction plan works like a charm: while everyone’s busy fighting, the Arkifane successfully steals the Tuchulcha Engine from The Rock, flees through the warp, and reunites all the fragments to create the Key (which turns out to be another esoteric machine called the Dissonance Engine). At long last, Abaddon and Vashtorr have the Key they’d been seeking throughout the Arks of Omen saga; they’ve won.

So, to summarise: at the outset of 10th Edition, the greatest Warhammer 40k chaos champion has a very powerful asset – the Dissonance Engine, known as ‘The Key’ – and is in search of ‘The Lock’ in order to get a weapon that’ll allow him to destroy the Imperium.

Bad news for Terra and the slowly awakening Emperor of Mankind; bad news for the newly returned Lion El’ Jonson, and bad news for the Imperial Regent Roboute Guilliman, primarch of the Ultramarines.

Boy, this sure would be a bad time for an old enemy like the Tyranids to suddenly attack on completely the opposite side of the galaxy from usual, worryingly close to Holy Terra, huh? Well, that’s exactly what happens next – just in time for Warhammer 40k 10th Edition to kick off!


Warhammer 40k Arks of Omen - Games Workshop image showing Ultramarines space marines fighting Black Legion Chaos Space Marine models in a Boarding Actions game

Boarding Actions

In addition to lore updates and tales that expand upon the events of the 41st millennium, the Arks of Omen books included new rules. However, unlike 2020’s Psychic Awakening story series, these new campaign books did not include wide-ranging Matched Play rules for specific Warhammer 40k armies.

Instead, Arks of Omen introduces an entirely new Warhammer 40k game mode, titled Boarding Actions. This mode sees players take smaller armies of 500 points into the Arks of Omen themselves, fighting room-by-room to achieve objectives, kill foes, and retrieve loot.

This game mode acts as a bridge between the larger-scale battles in Warhammer 40k 9th Edition and the smaller squad-based Kill Team system – while nodding at the earlier Warhammer 40k tabletop game Space Hulk.

You need two sets of the terrain from box sets like Kill Team: Into the Dark to play Boarding Actions, or you can buy a Boarding Actions terrain set for $210 / £130. There’s also a new Void War Bases kit for army customisation.

Players familiar with Warhammer 40k will find new restrictions forcing them to adapt their tactics and army composition in Boarding Actions. For a start, there will be no models with the Vehicle or Monster keywords allowed, making this very much a game for infantry units.

Warhammer 40k Arks of Omen - Games Workshop image showing Tyranids models in a Boarding Actions game

In addition, tight corners and small rooms mean long-range units may not provide much benefit. This means it may be a good idea to leave your missile-lobbing Eldar Dark Reapers at home and pack your roster with Striking Scorpions instead.

Warhammer 40k Arks of Omen - Games Workshop image showing Ultramarines space marine models in a Boarding Actions game

Arks of Omen Grand Tournament Mission Pack

The Arks of Omen narrative books coincided with a separate product from Games Workshop, the Arks of Omen Grand Tournament mission pack. This provided the missions and matched play rules for competitive Warhammer 40k, for the first half of 2023.

The Arks of Omen season brought several changes to the game. The Arks of Omen detachment made list building far more open-ended, making it easier to construct an army list however you like. As with previous matched play seasons, GW released a Munitorum Field Manual with updated points values for all units, and a Balance Dataslate that made tweaks to their rules. We’ve produced a rundown of the differences between the Arks of Omen Balance Dataslate, and the previous season of matched play.

Now that we’ve left the Arks of Omen behind and stepped into the wide blue yonder of Warhammer 40k 10th Edition, though, you might want to check out our fully updated guide to Warhammer 40k abilities; our 40k Leviathan review; or our favorite items from the 10th Edition Space Marines index rules.