Space Marine/Thunder Warrior Hybrids Confirmed As Canon?

It seems every fan has some small part of some franchise they're obsessed with. Some small part that we barely see, but people keep coming back to because of what they represent and the ideas they offer. While the Eldar Exodites are a personal one, for many fans of the Imperium of Man this comes in the form of the Thunder Warriors. Short-lived, violently psychotic and utterly unstable, they were utterly loyal to the Emperor while emulating many of mankind's worst traits.

While little more than a genetic stop-gap measure on the way to the more refined Adeptus Astartes, more than a few fans have developed a fondness for these hulking brutes. We know little of their victories or even culture save for what little was gleaned from the likes of the Outcast Dead. It seemed short of a few one-shots that Black Library was a whole were done with them. Well, sort of. Blackshields: The False War suggests something very, very interesting which might change a few things surrounding the lore of these mysterious figures.

While the audio drama itself is a fine one (and the rare example of a heist involving the Adeptus Astartes), the story dropped a surprising bombshell in the form of Endryd Haar. Nicknamed the "Riven Hound", Haar was the rare example of a World Eaters loyalist who had fully embraced his savage ways. While Captain Varren showed a surprising degree of nobility hinting as to what the legion could have become without the Nails, Haar was brutality incarnate. Willing to enforce his rule through executions, maiming and honour duels, all that was known was that he was Terran born and was one of the first of his legion.

Bit by bit, however, Blackshields added a few interesting details, seemingly building off of a statement from the Forge World rulebooks: "Endryd Haar and his three battle-brothers were part of the first initiate company of the XIIth Legion created in the Imperial Geneworks on Terra, long before his brethren had taken the name of the War Hounds, and many decades before they would become Angron's "eaters of worlds." Only he would go on to survive that company; a remnant of a lost age, a living weapon akin to his Legion brothers that came after and yet subtly different in his controlled savagery."

While this was initially put down to him merely being the first among their kind in a manner akin to Merir Astelan of the Dark Angels, the story kept going further and further with this idea. 

One of the first points cited very early on was his size, dwarfing even the Death Guard remnants among his force and surprising those familiar with the Legionaries. Then, along with his savage methods, it began to note other things, such as the fact he had no Nails. Instead, that his savagery and spite was born of something else:

"There were no Nails in his skull. His savagery comes from a deeper well."

This point is only driven further with a few hints surrounding Terra, that he effectively escaped from the place of his gene-forging, and later even his views on Horus himself. Determining that he must personally slay the rebellion's leader, he is driven more by a deep-seated contempt over anything we have seen with other characters. It's not so much betrayal or even the loss of his comrades as the nature of his act. A specific moment of which hinted heavily that this related to Horus having a far greater purpose planned than he had.

Even without all the above connecting this together, a man with notable inside knowledge of the Imperium's darkest secrets quietly asks him a very interesting question:

"Do you dream of thunder?"

Normally this would be the point where the article says "This is just a theory so please treat it as such" but given the sheer number of hints present here, it's difficult to say that this wasn't planned. Perhaps this is intended as a bait-and-switch or even an alteration to be built upon later on. Yet, with this all originating from one audio drama and all by one mind? That speaks less of different creative minds offering dots to join up and more of a plan. 

The question now surrounds just what Haar himself actually is. A missing link between the Thunder Warriors and Astartes, or perhaps even a variant of the older superhuman psychopaths implanted with Angron's gene-seed, forging a mongrel breed of warrior. Both are certainly possible, but you then need to consider other things atop of this. Particularly the subject of how the Thunder Warriors' bodies burned themselves out within a few years and even those left on Terra were on the verge of death.

The most obvious answer might be that Haar was a prototype, or a direct experiment. Master of Mankind threw in a questionable scene where the Emperor directly opted not to remove Angron's Nails due to the enhanced ferocity they offered, leaving many to question why he didn't just keep the Thunder Warriors if he sought such a creation. Perhaps he experimented with just that but disliked the end result.

With another Blackshields audio drama having already been announced and promoted, the chances are we might end up with a few more answers along with details surrounding this faction of Space Marines. Until then, we will just have to wait and think over the scraps of lore we have been given for the time being.