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Zael Effernetti, before being uplifted into the ranks of the Grey Knights, was an unregistered pyker taken in by Ravenor and his band. I really liked his interactions with Nayl who was clearly growing fond of the boy.

After becoming a Grey Knight named Hyperion he was instrumental in defeating Angron in the First War for Armageddon. It was a heroic act that earned him respect from the Space Wolves even as the Inquisition turned on them.

Now that we know Nayl was alive after the War for Armageddon I wish that somehow he had a chance to learn what Zael has become. Even though his memory was wiped it would still be nice for Nayl to see how strong he grew up to be.

The new warcom article about the design of the Malstrains talk about how their signal is so corrupted and unrecognizable that the Hive Mind effectively avoids Necromunda. Knowing this, could it be possible for the Imperium, or really any faction that understands this, to capture Malstrains and put them on multiple worlds (while still in captivity of course) to repel the tyranids from coming?

I find this whole era fascinating, especially the more “high science” eras reflecting humanity tech advance and mastery. Sometimes when I’m reading non-40k sci fi or fantasy I’ll imagine it’s set on some random world from DAoT or AoS! I’d love some actual stories or a collation of lore/myths from this time if such a thing exists (doubtful given the literary and in-lore mystique from this period is what makes it so interesting).

Anybody have anything?

After all the Ork incursions and Demonic hijinks, does Armageddon still gave a functioning civilization or is it all just a planet wide warzone?

Belisarius Cawl has almost everything Chaos would want and then some.

he has the Sangprimus Portum, access to MULTIPLE STCs, plus he created armor that healed Guilliman's body, plus he is hunting Blackstone to build another Blackstone pylon network, wouldn't it make sense to have almost every single chaos marine in the galaxy after the Archmagos?

In the words of Dr. Steven Strange "Chaos "could destroy life on a scale hitherto undreamt of" with the Archmagos killed, taken, or turned?

Also GW what an incredible idea for a campaign.

Belisarius Cawl has almost everything Chaos would want and then some.

he has the Sangprimus Portum, access to MULTIPLE STCs, plus he created armor that healed Guilliman's body, plus he is hunting Blackstone to build another Blackstone pylon network, wouldn't it make sense to have almost every single chaos marine in the galaxy after the Archmagos?

In the words of Dr. Steven Strange "Chaos "could destroy life on a scale hitherto undreamt of" with the Archmagos killed, taken, or turned?

Also GW what an incredible idea for a campaign.

Hey all! Had a quick question. I’ve been reading about the Dark Hunters of the White Scars who hung with the raven guard and adopted some of their tactics.

I then stumbled upon the Nemesis chapter of the Ultramarines who hung with the night lords.

Are there any other chapters any of you know of that hung out with other chapters and maybe adopted practices or tactics from them? I’d be interested to read more! Thanks!

I just finished False Gods and it was...not great to say the least. Of course following Horus Rising isn't an easy task but I still felt False Gods to have very weak characterization and Graham McNeills prose really felt like complete drivel most of the time. Not to say it didn't have some great moments. I'm still very excited for the rest of the series as I've heard a couple other authors come close to Abnett. Just wondering what I should be expecting from Galaxy in Flames, is it more Abnett or McNiell?

As far as I am concerned, blanks are immune to the warp and I am pretty sure the emperor wanted his Custodes immune to the warp taints. So why weren't custodes created as blanks?

I know it’s near universal to say the blue boys are the most effective and competent chapter in 40K but every time I hear someone talk about the “potential” of the dark angels in sort of hushed tones, it sounds like the kind of stuff that could literally like… save everyone.

Like if there is a chapter that has the stuff to just outright save the imperium and the emperor, it’s the Dark Angels. We may not know what said “stuff” actually is (cypher, the watchers, the rock, the Lion, their normal resistance to chaos, secret weapons, something else, etc) but they are the chapter most likely to have it. That the only thing really holding them back has been the obsession with the fallen.

Just finished it and i think it was great. Does ultramar ever find out the events that happened?

Wanted to make a post that serves as a reference for Tyranid naval capabilities. Since I feel the Nids space prowess is often understated. I'll mostly just try and convey what a standard Tyranid fleet can do. However, deviations are bound to occur, even in a faction as uniform as the Nids.

• Size:

So, of course we have to talk about the Tyranid fleet size. Surprisingly we do have a consistent figure for the number of biovessel typically found in a hivefleet. With the number most often sited being that of millions of bioships. However, in White Dwarf 225 it says, on the 50th day, that the numbers of space born creatures has reach 1.5 billion. Now the way I square that off with the far more consistent millions number. Is that space born creatures in the WD issue can also be in reference to attack craft, as normally during interstellar voyages these craft would not be present. In the Tyranids case this would include Harpies, Hivecrones and all manner of spore forms. Ultimately though whether its in the millions or billions it doesn't matter. Since, the only other fleet I can think of that reach this level of magnitude was Ghazkull's. For comparison sake, the 10 initial Indomitus fleets when put together number somewhere in the ballpark of a 1,000ships. With it being stated that the Imperium hadn't seen a gathering of vessel this large since the Horus Heresy. From the Dawn of Fire series:

"The Indomitus Crusade was the largest single military operation launched by humanity since the dawn of the Imperium, 10,000 years ago.

At the core of the endeavour were the great crusade fleets. There were ten of these planned to begin with, although fleets Octus through Decius did not finish their mustering until most of the others had departed. Each fleet was huge, compromising dozens of warships, many more transports and all the support vessels needed to supply them, so every fleet when gathered together numbered well over a hundred warp-capable vessels, and sometimes many more."

Meaning at bare minimum most Imperial fleets will be outnumbered a 1,000 to 1 in space battles against the Nids. That's also assuming that the number of attack craft doesn't increase the disparity by another 3 orders of magnitude. What's worse is that hilariously the number of Tyranid capital ships can still cliff this number. With their being over 50,000 Norncraft during the Devastation of Baal.

It should then come in as no surprise that even tendrils or splitters of a hivefleet can still be a formidable threat. And, why when a considerable chunk of a hivefleet is barreling down on a planet. Requires a massive expenditure of resources just to deal with. However numbers aren't the only thing in favor of the Tyranids.

Psychic Prescence:

The majority might know that the Hivemind helps the Tyranids coordinate strategies with a level of synchronicity rarely seen in other factions. However, many are still unaware as towards the true nature of the Great Devourer. With it being that of a psychic entity, whose power rivals even that of the Chaos Gods. If you're interested in dissecting that, I go further into detail about that topic here. However, how does this fact help hivefleets take on their opponents. Well for starters the same mechanism that allows Synapse-Creatures the ability to harness a portion of the Hivemind psychic might also exist for bioships, leading to the creation of Mindslayers. Psychic bioships who are capable of blasting away enemy vessels with Warp-energy or cause the crews of said ships to go mad, do to psychic induce hallucinations. Needless to say most faction don't have a good response to this. And while there's no denying that these vessel can be dealt with. The sheer amount of resources it takes to do so, is a risk in its own right. Then of course we have the Shadow in the Warp. The psychic barrier cause by the presence of the Hivemind blocking out all other forms of psychic phenomena. Not only is this an incredibly oppressive passive psychic ability that cut off psychic powers, communication and travel, but it also has other lesser known effects. Such as inducing a sense of dread that scales proportionally with the victim connection to the warp, the suppression of deamonic manifestation to the point of even banishment at time and even the disruption of non psychic tech. Finally one would be forgiven to think that the connection to the Hivemind might lead to the same weakness as found ground swarm. In which the elimination key targets such as Synapse-Creatures might induce great disruption through the Nids' command structure. Unfortunately for the inhabitants of the galaxy the Hivemind has found a work around for this problem that makes this weakness unexploitable.

Adaptability:

Something under appreciated is the adaptability of bioships. Often times this living armadas can adapt to stuff not even the ground swarms can. Capable of producing a vile secretion that hardens into diamond hard armor. That allowed them to resist temperatures below absolute zero and the bonus effect of making them resistant to Imperial battle fleet massed guns. This also isn't the only instant of bioships adapting to enemy vessel weaponry. With bioships from hivefleet gorgon becoming nigh on immune to Tau Ion Canons. Needless to say if the war of attrition wasn't going well for the opposing side do to the hilariously lopsided numbers advantage. It's definitely not going to get better if the Nids somehow find away to adapt to the enemy teams main weaponry.

Weaknesses:

Of course no faction in 40k is invincible and the Tyranids definitely have their own draw back. Their slower FTL means that despite their Shadow in the Warp ability cutting off Warp communication and travel. Particularly vigilant worlds in larger campaign still have enough time to amass resources and fortify before the Warp Shadow cuts them off. There also almost always an invading force, which is inherently is a harder position to take than defending one. Finally bioship, at least unaugmented ones, have poor armor and are typically slower than their prey. Leading to them easily being dispatch in most naval engagement. Not the worst problem to have when you out number your enemy at least a 1,000 to 1, but still a weakness non the less.

Conclusion:

With all of this laid out. I think it's easy to see why, despite having all the chapter of the blood reunited. The Blood Angels where quickly overrun by even just a tendril of the Leviathan.

What be the verdict on this particular perplexing puzzle?

I feel inclined to say that considering their oft ‘You mere humans’ and the VERY unnatural amount of surgeries and enhancements, they’re not human. Perhaps partly so, a neo-human, but not a human as we baseliners would adequately understand or be able to relate to.

What do you think me hearties?

I've never understood why the split happened to the extent that they would worship chaos, it represents everything that they stood against.

How can you optimise or make production lines, if there's a constant random chance of a Daemon Engine taking control and ruining everything... At least with the initial AI constructs, they didn't have this sort of issue.

is/was the procedure different between those that were firstborn astartes who became primaris versus those that were regular unaugmented humans that became primaris? always wondered why a distinction was made here?

One of my favorite factions in 40K is the Dark Eldar. Downton Abbey with knives, the fae courts in space, hellraiser cosplayers, unapologetic mustache twirling villains, the Drukhari are just plain fun. I've also noticed a LOT of confusion about them, including basic context like the everyday life and experiences of a Dark Eldar. A notable element of their biology is that they feed on pain and suffering. Literally standing near someone in pain provides a Dark Eldar with vitality and energy. In addition, their medical sciences are near perfect. For that reason, a suitably wealthy Dark Eldar can expect to live... forever. Dark Eldar society is mainly based around the Kabals, a cross between a private army, noble court, and den of thieves. As a result of their long and decadent lifestyles, they tend to have incredibly complex social and political systems. Theirs is a world where the outfit one chooses to wear to a court dinner can cause a chain of events that leads to the deaths of millions.

Lord Malwrack is an Archon, and the ruler of his Kabal. He is ancient beyond belief, yet powerful. Archons are the ruling class of their society, occupying the upper echelons of power within their Kabal, and within Malwrack's none can challenge his supremacy. This excerpt begins at the one of the most important social events for the Drukhari, the gladiator games. Part buffet and part opera, everyone who is anyone will make an appearance at a particularly promising matchup.

Lord Malwrack was rich, powerful and emotionally dead inside. Even though his was a race renowned for their passions and lust for life, time had tempered him. With every passing century he became all the more desiccated, both physically and spiritually, until all that remained was a perpetually scowling, slightly hunched old man who treated each new day with a dismal contempt. It therefore came as a great surprise when he suddenly found himself in love.

Malwrack and his daughter, Sawor, had been attending one of Commorragh’s endless gladiatorial games and their box seat, perched high along the curving wall of the arena, offered them a spectacular view. Sawor watched with rapt interest as below her the combatants slashed each other with razorsnares, eviscerated each other with hydraknives and turned one another into large cubes of bloody meat with the aid of a shardnet. She was young and vigorous, and her senses were sharp. Even from so far above the killing floor, Sawor could smell its erotic mixture of sweat and blood, could taste the fear and adrenaline steaming from the participants, could see the detail of sinew, flesh and bone in every severed limb.

Malwrack, on the other hand, had long ago lost most of his senses. It happened with eldar his age when they let themselves go. Taste, touch and smell were greatly diminished now, as if coming to him from behind a thick blanket. Even his sight was cloudy and, grunting in dissatisfaction and submission, he reached into the folds of his robes and withdrew an ornate pair of opera glasses. For a time he too watched the ballet of carnage below, but it didn’t bring him the same exhilaration as it did Sawor. Malwrack had seen such wych-work hundreds of times before on worlds throughout the galaxy. At first he felt only a deep malaise, but as his daughter began to cheer more loudly, he felt something else: envy.

He felt that quite a lot these days, truth be told. Well aware of his own infirmity, he hated nearly everyone around him; hated them for their youth. The one exception was Sawor. She was the only person in his kabal to whom he might extend forgiveness for an attempted assassination or coup. The mere thought of her made the wrinkled corners of his mouth twitch; the faintest echo of a smile. Of all the things he owned, of all the people who served under him, she was his most favoured. There was a word, a single word, used by the other, lesser inhabitants of the galaxy to describe this feeling, but it escaped his aged brain at the moment.

Malwrack’s attention drifted from the fighting, and he began to look around the stadium. His wandering gaze eventually turned to the other box seats where the Dark City’s social elite sat. One came to the theatre to be seen after all, and he idly wondered who was here today.

Suddenly, he stopped and sat upright. Halfway across the arena sat a woman. She was alone, flanked on either side by a pair of stalwart incubi bodyguards. Her black hair, shot through with grey, was piled high atop her head and spilled around her neck and shoulders in thick waves. Her skin was flawlessly pallid, stretched smooth and tight like a drumhead. Her eyes were dark and luminous, her lips painted obsidian. As she reclined into her throne-like chair, Malwrack saw that she wore a form-fitting suit of armour with leg greaves shaped like spike-heeled stiletto boots, and an upper section that was more like a bustier than a protective chest plate. Black evening gloves ran from her tapered fingertips to her elbows, and the train of a charcoal dress with multiple layers flowed around her. A large pendant, obviously a shadow field generator, nestled between her pale breasts.“Who is that?” he breathed.

...

Malwrack watched intently as the mysterious woman sipped from a goblet. Everything about her seemed to crystallise for him: the sensual, languid way she swallowed, the colour of her fingernails as she brushed a lock of hair from her face, the slight pulsing of the drug injector tube that ran into her jugular. It was as if the longer he observed her, the younger he became. His body stirred, pulse flaring, muscles tensing. He licked his lips, salivating for the first time in a decade. Something was washing over him in a sudden wave, a feeling that had been absent from his life for so long that he shook as if electrified. He knew then, without question, that he had to have this woman, had to impress and then utterly dominate her. His sole purpose in life now was to make her his cherished yet personal property. He was head over heels in… what was that word the mon-keigh used?

The woman furrowed her brow suddenly, cocked her head to one side, then looked directly at Malwrack. The old archon gasped and dropped his glasses. He awkwardly gathered up his belongings, and hurried out into the hallway.

...

There is a slight time skip here. Lord Malwrack has decided that this woman, this mysterious beauty, will be his. His heart aflame with passion for the first time in uncountable eons, he sets about wooing her. After decapitating all his romantic rivals and delivering them to her sitting room failed to impress, Malwrack decides to deliver a grander gift. I'll let the story summarize

...

The planet Franchi was cold, its days rainy and its nights foggy. It was covered in sweeping mountain ranges, dense forests and churning oceans of grey foam. In short, it was a world that any Dark Eldar could appreciate, and Malwrack was determined to present it to Baeda as a gift. In fact, Franchi had only one flaw: there were humans living on it. So, the old archon got to work.

...

Buildings burned out of control. Dead Guardsmen and destroyed vehicles lay scattered about. A single bunker remained; its solitary door had been wrenched free.

Within it, his warriors reported, a handful of scared refugees had holed up in the hope that they might be spared. Lord Malwrack descended a narrow set of concrete steps into a damp, square room littered with blankets and pre-packaged food wrappers. The only light came from a few dim panels set into the walls. Four dead bodies lay splashed across the floor, the handiwork of his sybarites. The last two survivors had been reserved for him.

Malwrack assessed them quickly: a male and female, dressed in soiled, khaki uniforms accentuated only by identification tags around his neck, and a diamond ring on one of her fingers. They sat in a corner with their arms wrapped tightly around one another. The female buried her face in the man’s chest, muting her sobs. He in turn rocked her gently and tried to whisper soothing words of comfort.

“Well,” Malwrack said joylessly. “Best get this over with.”

In the name of expedience, he pulled his pistol from its holster, intending to shoot the female. Then, quite unexpectedly, there was an explosion of movement as the man launched himself forwards. He grabbed Malwrack’s left wrist, bending it upwards, and a cloud of splinters tore into the ceiling. In a single motion Malwrack slammed his forehead down onto the human’s nose, jerked his knee into the man’s stomach, and drove an elbow into his back when he doubled over. Malwrack effortlessly shifted his weight, and kicked him square in the chest. The man’s body collapsed against a computer display screen. Glass shattered and sparks flew. Malwrack leapt and drove his bladed glove through flesh, bone and concrete flooring. He snorted loudly as he inhaled the man’s escaping life essence.

This, it seemed, was finally enough to snap the female out of her paralysis. She ran over to her partner’s body, howling, and draped herself across it.

He chambered another round into his pistol, and looked down at the female. “He doesn’t deserve so touching a tribute as your tears and wails,” he said to her. “Why do you weep for such an insignificant man?”

She glared at him with her cornered animal eyes. “He was my husband,” she roared. “I loved him!”

Malwrack suddenly brightened. He snapped the fingers of his gloved hand, and pointed at her with one of its talons. “That’s it!” he said with glee. “That’s the word I’ve been trying to remember. Thank you.”

I am back with a review of latest stuff.

My hype levels for this novels were somewhere at medium levels. I am aware Lyons wrote some decently received Krieg novels already and I was curious about the Krieg and Vraks because the community (and youtubers) talk about this non-stop, but they are pretty scarce in actual novels. A negative, for me, is that while I still like them the IG are my least favourite faction and in usual circumstances I would skip this novel, but BL releases became rare lately so I decided to try this novel out.

I would say this novel is very good. The characters are interesting, the plot is interesting, at all times it kept me hooked wondering what will happen next and the lore about Krieg is delivered very well as a part of the novel without feeling like exposition. There is fun character progression for the characters and the Krieg as a whole. I would recommend it to everyone and if you are a Krieg fan especially. The novel is very grimdark, but never grimderp in my opinion.

Spoiler thoughts:

!After the prologue where an Imperial Assassins try to kill the rebel cardinal on the world and fails which really sparks the rebellion the novel covers the entirety of war for Vraks by focusing on major Krieg actions in the war. The involvement of other major military factions like GKs, SMs and titans is just briefly described in war reports. The first major action is one of the earlier attacks in the first years of the war where a Krieg is only survivor after one attack and he earns his name Tyborg (Kriegs have no names before gaining high enough rank where they gain one because officers need for the Imperial administration) and he is one of the characters we follow. He meets a confessor which is another main character in the story alongside the leader of the Krieg on the world which gives us a PoV of a "normal" Krieg officer. The Krieg are very loyal and motivated, but she believes they also need individual heroes to inspire them further and she argues that with Tyborg and the Krieg as a whole.!<

!There are some more military actions, first appearance of CSM on the battlefield followed by a quick response by Dark Angels and a fun subplot of a local Vraks traitor who turns sides covertly, but then is discovered and after questioning allowed to remain a Krieg the novel really peaks in the finale. The final stages of the battle are especially bloody and an especially bloody part is under command of Tyborg and he and his mean break after an appearance of a bloodthirster. This by some is attributed to the individualism of Tyborg inspired the confessor and there is some interesting "negative" character development by the Krieg who from there stop using names for their officers and to be more grim and determined. Tyborg himself is about to be court martialed and accepts his fate, but Inquisitor Lord Hector recognizes he is a hero and that a normal man breaking before a bloodthirster is unsurprising. Tyborg is invited to join his retinue and he accepts because of the confessors lessons how Imperium needs heroes which hints at a possibly interesting sequel.!<

I see a lot of art with those body ports on Custodes and Sisters of Battle, and I keep seeing it go both ways on whether or not all people who use power armor have them.

On the one hand, I hear a lot of people say it's the Black Carapace and those ports shouldn't be on anyone besides Space Marines.

On the other hand, I see models like the Repentia Squad and see ports of a similar nature.

So which is it? Finding official word on this has been a pain in my arse for about a year now.

note order of speech here: i do not mean "what is written on purity seals" that's simple, prayers, symbols, oaths of moment, lots of stuff

but rather i am asking: what material best suits them, parchment paper stands out to me, but the flowing look of seals in many art pieces almost resembles fabric, some kind've cloth perhaps

do you guys think it matters for accuracy if a seal is printed on paper or cloth?

if so, which do you feel best suits the seals in your opinion/as per the lore?

for context: i'm just making some for personal use, but wanna nail the vibe down

Listening to Carcharadons: Red Tithe. Thought it was really cool when the Arbitrator is trying to communicate with them for the first time. Unsure using high gothic. Not really understanding what he’s saying. I thought it was a cool instance of how far removed humanity is from the Astartes, especially chapters like the Sharky boys.

Cold Open Stories Fast Fiction contest is in full swing! 

Unlikely Allies challenges authors to craft an original Warhammer 40,000 short story revolving around conflict and cooperation. Whether it’s ancient enemies joining forces against a greater evil, or individuals from vastly different backgrounds finding common ground, stories should highlight the tension, drama, and potential for growth that these unexpected partnerships bring.

A panel of community judges will score each entry, with up to 15 submissions being published on coldopenstories.com.

Check out the guidelines below:

• Stories must be 1,000 words or less

• Follow the theme – 'Unlikely Allies’

• Write according to Faction Restrictions

• Have your entry submitted by September 1st, 11:59PM PT

Complete guidelines, faction restrictions and the submission email address can be found in the Submissions section of the Cold Open Stories website under the Warhammer 40,000 imprint.

I know that it is the minimum zone safe distance to enter warp space(Not have your ship damaged by gravity of the star, not getting civilian populations insane because of a warp hole open in the middle of their sky etc) , however, a few questions arouse.

• It is an actuall point like the La'grange points, or it is more like a zone surrounding a star?
• Is harder to enter binary or trinary systems due to the gravitational fluctuations?
• How do a Imperial ship finds a system in the warp?

https://youtu.be/lNspMmPzEb0?si=Td0Wubcljn4qZGqE

Am I reading into this too much? Are some space marines prisoners?

It looks like this guy is being kept as a prisoner and only being used when the imperium needs him.

I've really enjoyed the first book, and while I felt the second had some plot/pacing flaws, it was a good read as well. I have looked a bit about what was said in the past regarding the very ending of the book, but nothing helped me understand it fully - so here go spoilers:

!What was the purpose of the weapon? From what I understood, the first time it was fired, it was a terrible thing, and played a big part in the spreading of the Flayer virus. And Unas calls himself the God Eater, a detail not to be overlooked. !<

!But what did the weapon do the second time? Reveal the planet to [whoever is the Ithacan King], so they may descend? !<

!What's with the city and the palace? !<

!There are ships from every dynasty around the planet, all empty. Where did these other, supposedly flayed necrons go? If the weapon is needed to penetrate the mist, then they couldn't get down there, so Oltyx should be the first Flayer King?!<

From my series of questions I'm sure you can get the collective gist of my questions. I like endings open to interpretation, but this one was more confusing than intriguing to me

I know I'm probably gonna be labeled as the noobest of noobs, but I'm looking to continue my Horus Heresy journey. I read Horus Rising and read False Gods. Can anyone point me to the next few titles, chronologically or story wise, that I should read next?

Please don't be too harsh, thanks for all the advice, and as always, Emperor Protects!!!

I’ve been reading Knights of Macragge, and it’s left me with a few questions. For those unaware, the book starts out on a ship lost in the Warp after the Astronomicon flickered.

1. Why couldn’t the ship get back on course after the Astronomicon came back on? The book never mentions anything like a Warp Storm, so there doesn’t seem to be conditions that would block it. I was under the impression that the Astronomicon is like a giant blazing beacon in the Warp—shouldn’t the Navigators be able to see it even if they’ve sailed far off course?

2. Why is it so difficult to get out of the Warp? Why can’t the captain push the De-Warp button and pop back into realspace?

Thanks for the help!

I just heard it was a tomb world, and I have not heard anything else. Can anyone please tell me more? Please?

["Spoiler text."]By the time the Emperor and Horus battle on The Vengeful Spirit, all of the traitor primarchs are out of the picture. Lorgar and Curze never made it to Terra, Fulgrim decided to focus on hedonism, Perturabo noped out of the Siege, Omegon is being mysterious as usual, and Mortarion, Angron and Magnus were banished to the Warp.["Spoiler text."]

Was this narrative choice necessary for a proper conclusion to the Horus Heresy/SoT? Overall, I think it was although that choice does raise a couple of lore concerns.

On the necessary side:

Removing the traitor primarchs reinforces the father vs favorite son theme of the climactic battle. It's called the Horus Heresy, after all. The Emperor and Horus face each other without the support of any other primarchs on their side.

The removal of the traitor primarchs helps keep the loyalists in the game until the end. If Perturabo had stayed on Terra or Fulgrim held the Saturnine Wall or Mortarion had kept control of Lions Gate Spaceport, there might not have been any climactic battle on the VS.

The absence of the traitor primarchs means there is no focal point to rally the traitors after Horus falls ensuring that the loyalists are able to clear the traitors from the Sol System.

Lore questions:

Older lore certainly either states or implies that all the traitor primarchs were on Terra until Guilliman arrives. I got the impression from the World Bearers Omnibus that Lorgar was present, for example. There is nothing in the lore before the SoT to indicate that other traitor legions are mad at the Iron Warriors for abandoning the field. While I think these are valid concerns, overall I understand why the authors took the direction they did.

Thoughts?

Edit: Spoiler tags added

And when I say reclaim, I also mean them purifying those worlds for future use.