Henry Cavill’s Warhammer 40K series should ditch Space Marines for one of the series’ most important characters, and I know exactly how it would work

When most people think of Warhammer 40,000, they think of the hulking Space Marines, particularly the bright blue Ultramarines. This is understandable, as they're often front and centre of Games Workshop's marketing, and stellar series extensions, like 2024's Space Marine 2 game, have only deepened this association.

So when it was revealed that actor (and 40K superfan) Henry Cavill would be starring in a Prime Video series based on the Warhammer 40,000 universe, many fans assumed he'd be playing a Space Marine, or at least something connected to them.

Some speculated that Cavill could play a character like Titus, who is the protagonist from the Warhammer 40,000: Space Marine game series, while others thought he may even be playing the Emperor of Mankind or his treacherous son Horus.

This was entirely reasonable, especially after Games Workshop's epic sixty-novel Horus Heresy series ended only relatively recently, re-establishing the franchise's background lore, and spawning the "30K" Horus Heresy tabletop game, which is set during that conflict.

Others believed that Cavill could be playing Roboute Guilliman, the Primarch of the Ultramarines, the first of the Emperor's loyal sons to return, and arguably, the closest thing 40K has to a protagonist. Guilliman, too, would be an excellent choice.

The Inquisitor will see you now

However, as tiny snippets of information trickle out about the upcoming streaming series, the evidence is starting to support another theory – that Cavill won't be playing a supersoldier like a Space Marine, a Primarch, or the Emperor, but a human. And not just any human, but one who's become a firm fan favourite, and a character who is entrenched in some of 40K's most important storylines.

We're talking about Gregor Eisenhorn, an Inquisitor who's the star of multiple books and also has his own tabletop model. Eisenhorn's job is to sniff out corruption by Chaos (essentially Warhammer's version of Hell and the otherworldly force that corrupted Horus), then deal with it accordingly, and often ruthlessly.

While Eisenhorn started out as an Inquisitor who did things by the book, his increasingly complicated story has seen him take a more radical approach to protecting humanity, and one that often puts him at risk of corruption by Chaos. As a result, he's seen as a rogue when compared to his fellow Inquisitors.

But while Eisenhorn hasn't quite entered anti-hero territory yet, he'd still be an ideal choice as the complicated and morally grey protagonist of a Warhammer TV series. And it's looking increasingly likely that this will be the role Henry Cavill plays when the show starts edging into view.

Of course, this is far from confirmed, but the stars are starting to align that way. For starters, a show that followed Space Marines primarily would be very expensive for a studio to make. It wouldn't be impossible, but focusing the action on eight-foot-tall supersoldiers battling Tyranids and Orks may be a bit ambitious for 40K's first live-action outing.

However, a more human story focused on intrigue and the subtle but insidious nature of Chaos could be incredibly compelling, and Eisenhorn is the most obvious candidate for such a story. It would also show the audience that there is so much more to 40K than Space Marines. As epic as they are, they exist to protect humanity, so let's see some actual humans once in a while.

More evidence for this casting comes from Eisenhorn's creator, the author Dan Abnett. When asked about Pandemonium, the next novel in his Bequin series, which is a spin-off from the Eisenhorn books, Abnett revealed he is under a non-disclosure agreement with Games Workshop and cannot talk about it.

The delay of the Pandemonium book has baffled many Warhammer fans, but if elements of its story are being adapted for TV, then this could explain why. It also lends more credibility to the theory that Eisenhorn will be involved in the series, and most likely played by Henry Cavill.

This brings us to the final piece of the puzzle. The adventures of Bequin and Eisenhorn have seen both characters on the trail of the mysterious King in Yellow, whose identity was revealed in the last book of the series. This character was once known as Constantin Valdor, who was the Emperor's bodyguard during the Horus Heresy and like a brother to his actual sons, the Primarchs.

For reasons unknown, the now 10,000-year-old Valdor is searching for the means to take control of the Emperor – and therefore humanity – with Eisenhorn and his allies racing to stop him. Valdor's intentions, and what could happen if he succeeds, could have galaxy-shattering implications, and Eisenhorn might be the only person who can prevent this from coming to pass.

This essentially makes Eisenhorn one of the most important players in all of Warhammer, and if Cavill has indeed been cast in this role, it means both fans and newcomers are in for one heck of a ride – and without a Space Marine in sight.

For more check out our guide to the best new TV shows coming your way for the rest of the year.