The beginning of the game will serve as a flashback episode of sorts
Perhaps in the first hours, more or less, we will see Titus in service to the Inquisition (years before the events of the current game)Titus may first be seen as a firstborn marine, before events cause his transformation into a Primaris Marine.
There will be a Mêlée à Trois halfway through the game
Much like the first game with the Orks, you will just fight the Tyranids until about halfway through until the second army (Necrons, Dark Eldar or maybe even Chaos again) will show up and start to wreck both factions.- Confirmed: The second faction is the Thousand Sons chaos legion, revealed by the Extended Gameplay Trailer.
The Swarmlord will be the final boss of the game
As a prominent Tyranid lifeform engineered for close combat, not to mention the long history it has with the Ultramarines, it would make sense for the Swarmlord to be the final boss, as killing it could be the way to end the Tyranid threat on the planet. Genestealer Cultists will be present as a secondary enemy faction
This would make sense, as the cult serve as the vanguard of the Tyranids meant to compromise and weaken the planet's inhabitants to make it easier for the Tyranids to invade and devour. Hive Worlds in particular happen to be one of their favorite dishes on the menu, and a perfect breeding ground for Genestealers.- To add to this, from a gameplay perspective it would add enemy variety.
A possible Horde Co-Op Multiplayer Mode
Since the developers also made World War Z: Aftermath, they could have a multiplayer mode similar to that game (and like Vermintide/Darktide). And we will play as Deathwatch Space Marines. Drogan's Power Source will make a return
Warhammer 40,000: Boltgun had the Power Source as a plot element that was eventually recovered by the end of that game. If Space Marine II is set during the 4th Tyrannic War, then the Power Source may be used again as a sort of last ditch effort to combat the Tyranid splinter fleet. There will be a sort of Psychic Scourge 2.0, and this time it will be successfully used against the Tyranids. The Thousand Sons and Nemeroth will be the second enemy faction
The Co-Op Trailer implies the presence of Tzaangors and chaos portals. If that is the case, then the Thousand Sons will be the secondary antagonistic faction. And if Power Source, as mentioned above, will be a plot element in the second game, then Nemeroth will make his return to once again try to claim it for himself.Nemeroth might either be manipulating the Thousand Sons forces, allied (at least, initially) with the commander of the invading Thousand Sons forces, or it will be revealed that Nemeroth and his warband were a splinter warband of the Thousand Sons (or was once a member of the Thousand Sons before starting his own warband composed of non-Thousand Sons marines)
- Partially confirmed. As of the Extended Gameplay Trailer, the Thousand Sons are in the game. Nothing yet of Nemeroth.
The Thousand Sons aren't actually the secondary enemy faction
The trailer indicates that Titus was pulled away from some kind of crusade to fight the tyranids. So perhaps rather than the Thousand Sons revealing themselves as the new enemy partway through the game like last time, they're actually the Starter Villain for the game that he was facing as a form of trial to prove his loyalty.