Which fallen primarch has the greatest potential...

[Iron Father Ferrum]

Ferrus comes back as a daemon. Guess I’ll have to start collecting chaos then

Ferrus' warp ghost appeared leading the warp ghosts of slain Space Marines and Imperial soldiery in Master of Nankind. If he comes back, the groundwork is there for him to come back leading the Legion of the Damned.

[Withershadow]

Eh... those were the Emperor's psychic manifestations of all the people who have died for him, not sure how stable that platform is for a return.

[Claws and Effect]

The specific wording wasn't turn traitor. It was specifically "May not come back on the same side".

 

That leaves it open for a Primarch to come back and break off from the Imperium because they are just that disgusted with what it has become, while remaining loyal to the Emperor.

Edited February 16, 2018 by Claws and Effect

[bushman101]

I think Magnus could turn. Tzeentch is the god of change, maybe that could mean a change of loyalties. He could be loyal and yet still be a unwitting pawn of Tzeentch.

 

The Lion is a obvious choice for a traitor, but it could be a unwillingly choice.

He goes after the Fallen, and friendlies get killed. The cover up just makes bad worse and he is declared Perditia. He is loyal after a fashion, but is cast out of the imperium

Edited February 17, 2018 by bushman101

[Noserenda]

The Daemon primarchs are all effectively dead and reborn as a fragment of a chaos god, which basically rules them out, which only leaves Alpharius (Omegon) or a returned from the dead Night haunter (Which seems unlikely)

[Ishagu]

Alpharius/Omegon is really the only one with potential to return as a loyalist. It would also be pretty awesome and could have little to no impact on Chaos Alpha Legion. They can function without a singular leader, it has been hinted that Omegon has lost control of the Legion, etc.

[Wulf Vengis]

Perhaps a shard of Magnus returns as a loyal entity.

[b1soul]

We already had that...Janus

[Jorin Helm-splitter]

Well the big four are out (Magnus, and Morty have models, fulgrim is a crazy snake person, and well Angron is Angron). Lorgar is in the current fluff leading his legion and an arch priest, Petrubro has a fortress in the eye, Cruze and horus are dead. So that leaves Alpha Legion as really the only the option on the fallen side.

 

Loyalists - there are a lot of options more so when you consider that they may just want to do things differently than Guilliman. Multiple Imperium fractions would actually be good for the game too. 

[Kinstryfe]

Hmm. I have a hard time thinking any of the Primarchs would fully switch /sides/ on the Chaos/Imperium scale. Unless there's some huge retcon, most of the current Primarchs have been portrayed as complicit and dedicated to their own side. (When Horus killed Sanguinius most of his soul was taken captive by the Chaos gods! A tiny bit escaped to become the Sanguinor, but the rest has been corrupted and tortured over ten thousand years to turn him into Sanguirion, the Angel of Chaos!!!). I used to think that Fulgrim may be redeemable, since his fall was as much to do with possession as anything, but I believe I read that in later novels he shakes it off and is still just as Fulgrimy. I can't see Russ, Corax, Vulkan, or Dorn easily falling to chaos. The Khan would have back in the day if he was gonna. Maybe, mayyyybe I could see Magnus being an agent of Tzeentch but helping the Imperium at times. Tzeentch is known to play the long game, and what helps him against his brothers is not necessarily always going to be against the interests of the Imperium. The Lion is kind of an odd outlier. He's a loyalist despite being marked by chaos as a test tube baby. On the one hand, he was /supposed/ to fall, and half of his Legion did. But on the other, I've come to really like his strength of character: that he was marked early by the ruinous powers and was the only one of them to actually resist them and stay loyal. Him turning would be way too cliche.

 

Of course, this leaves "Alpharius". It would actually make sense for them to release a model a bit smaller than Guilliman for the Alpha Legion who can be used by both Chaos and Imperium forces, and would be the one Primarch to be for an unexpected faction that would make sense from the story thus far.

 

Though if being with a different army is taken a little more flexibly, there's a lot of options. Resurrected cloned Mechanicus Ferrus. Crusading Black Templars Dorn. A returned Corax who hates what the Imperium has become and his children being complicit in it, who takes to the battlefield alongside Militarum regiments to try to fight for the little guy. Lots of interesting ideas there that could technically fit the bill.

[Lord_Caerolion]

Well, there is the rough theory of a third Primarch of the Alpha Legion, at least in the Forge World Horus Heresy books. The Hydra does have three heads, after all.

[Kinstryfe]

My conspiracy theory sort of cobbled together from the Alpha Legion blood drinking stuff they did in a novel is that the Alphas have a crazy active omophagea, and that their Primarchs can literally survive by basically overwriting one of their Astartes. "I am Alpharius" is less about secrecy than potential; when one Primarch falls, he can be resurrected in one of his Astartes. Thus the secret war between Alpharius and Omegon has played out thousands of times over ten thousand years, because the only way to truly kill the Hydra would be to remove all of its ten thousand heads, because it can regrow from even one.

[Withershadow]

My conspiracy theory sort of cobbled together from the Alpha Legion blood drinking stuff they did in a novel is that the Alphas have a crazy active omophagea, and that their Primarchs can literally survive by basically overwriting one of their Astartes. "I am Alpharius" is less about secrecy than potential; when one Primarch falls, he can be resurrected in one of his Astartes. Thus the secret war between Alpharius and Omegon has played out thousands of times over ten thousand years, because the only way to truly kill the Hydra would be to remove all of its ten thousand heads, because it can regrow from even one.

They also have psychic techniques that accomplish similar ends, overwriting a person's personality and "replacing their soul with that of another", so that is certainly plausible.

[Huggtand]

As Claws and Effect said there is the option that loyal Primarch don't fall to Chaos but go independent instead. Think of the delicious irony if the Lion came back and create his own empire 

[sarabando]

As Claws and Effect said there is the option that loyal Primarch don't fall to Chaos but go independent instead. Think of the delicious irony if the Lion came back and create his own empire 

I would have loved to have seen this, Berty G holding the southern empire and Lion el keeping the north.

[Chapter Master Valrak]

 

Ferrus comes back as a daemon. Guess I’ll have to start collecting chaos then

Ferrus' warp ghost appeared leading the warp ghosts of slain Space Marines and Imperial soldiery in Master of Nankind. If he comes back, the groundwork is there for him to come back leading the Legion of the Damned.

 

 

I must have missed this, what happened?