Warhammer 40,000: Space Marine 2 fans have a good idea which enemy faction they will be fighting in Space Marine 3

Warhammer 40,000: Space Marine 2 is now over a week old, players have completed the campaign and are starting to get acquainted with the co-operative Operations mode and the PvP mode Eternal War. But fans are already speculating about which enemy faction they'll face off against in the seemingly inevitable Space Marine 3 – and based on in-game clues, there can only be one choice.

Warning! Spoilers for Warhammer 40,000: Space Marine 2 follow.

Space Marine 2 sees Titus of the Ultramarines take on the Tyranids and the traitor legion of the Thousand Suns. The campaign ends with a massive battle against a daemon army and even a trip into the Warp. With the help of Marneus Calgar, Chapter Master of the Ultramarines, Titus successfully fends off both enemy factions before being sent on a mysterious mission that hints at the continuation of the story in yet another sequel.

This sequel – let's take Space Marine 3, since the runaway success of Space Marine 2 suggests that developer Saber Interactive will indeed make more games in the series – is sure to feature the Necrons, the immortal skeletal robot xenos from Warhammer 40,000. Why do fans think the Necrons are next, after the Orks of Space Marine 1 and the Tyranids and Thousand Sons of Space Marine 2? There are clear indications that the Necrons will be hidden in Space Marine 2 itself.

To set the stage: A mission that takes Titus and co. deep into the bowels of an alien planet features ancient and mysterious wall markings that are a clear reference to the Necrons.

There's even a dataslate (audio logs from Space Marine 2) that reveals that Necron constructs have been killing Techpriests. You can see these constructs lying around everywhere (the one below looks like a Canoptek Tomb Stalker to me).

This clue is part of the third act of the campaign, where Titus heads to a Necron tomb world filled with Necron buildings and technology. Some players even suspected, given the nature of the mission, that the Xenos would make a surprise appearance as a third enemy faction in the campaign.

In fact, the story of Space Marine 2 revolves around the Necrons. The Techpriest, who is off track, attempts to use an ancient Necron artifact to neutralize the influence of Chaos by sealing off the Warp, the hellish dimension from which Chaos erupts. At least, that's what the Techpriest thinks the artifact does (it doesn't, then it does).

Assuming the Necrons do show up at some point, they're likely to be very angry. As a faction, they have a collective “got up on the wrong side of the bed” attitude, having awakened from a 60 million year slumber beneath the feet of the Imperium. They'll probably have something to say to the Adeptus Mechanicus banging on their door during the Space Marine 2 campaign, that's for sure.

As for Titus, he will no doubt be called upon once again to save the day. He will fight Necrons and the forces of Chaos with the kind of enthusiasm we have come to know and love, but Chaplain Leandros will keep a close eye on proceedings, just in case a whiff of corruption arises. Honestly, give poor Titus a break, will you? Perhaps we can get the Ultramarines' Primarch Robute Guilliman to speak for himself.

This is all very exciting for Warhammer 40,000 fans, but unfortunately we'll have to wait for a story expansion or Space Marine 3 to find out what happens next. Space Marine 2 has delighted over two million players and, according to its developers, sold faster than any Doom game. It's already the most played Warhammer 40,000 game of all time, according to Steam competitors, and could grow even further when DLC finally becomes available.

We have a lot more to report about Space Marine 2, including details on Roadmap after launchthe upcoming introduction of class customization for co-op mode after Players found themselves in a class conflict before the missions in Operation Modeand a report about those creepy flying babies that you keep seeing on the battle barge.

IGN's review of Space Marine 2 gave it an 8/10. We said, “Warhammer 40,000: Space Marine 2 may not break the mold of third-person shooter classics, but it looks fantastic, makes good use of Warhammer lore, and features brutal combat that just feels great.”

Wesley is IGN's UK News Editor. You can find him on Twitter at @wyp100. You can contact Wesley at [email protected] or confidentially at [email protected].