Warhammer 40,000: Darktide is following in the footsteps of the Vermintide series, which are four-player co-op games where players choose from various thematically appropriate classes. While we saw an ogryn, a zealot, and two veterans in the release date trailer, a cover story in the latest issue of Edge Magazine confirms a psyker will be another option.
In the 40K universe, psykers are able to reach into the parallel universe called the warp with their minds and draw on its power to essentially work magic. It's risky, because the warp is where Chaos comes from: a sentient, malevolent force that manifests as daemons. The Inquisition hunts rogue psykers before they cause too much damage, and recruits the strongest of them to join the ranks of the Sanctioned Psykers.
As sometimes PCG writer Alex Wiltshire writes in Edge #372, "The Psyker is an unstable magic user who, if they overuse their powers to pop heads, will succumb to the perils of the Warp and explode, similarly to the way Sienna, Vermintide's wizard, does."
Darktide's psyker can also use the power of the warp to protect against incoming ranged attacks, though it seems every class has a similar shield, with the veteran protected by armor, the zealot by the power of faith, and the ogryn by sheer thickness. All of the shields encourage grouping up by recharging faster if you're close to other players.
While the classes in the Vermintide games are five distinct existing characters, in Darktide players get to personalize them, personalizing their own loadout and face. "Fatshark hasn't designed a character creator for its previous games," Alex writes, "but the system incorporated here ably allows you to construct the scarred and mutilated grimdark hero you always wanted to be."
That might explain why we've seen two different veterans in the promotional material. Perhaps they're two versions of the same class, with different cosmetics and gear?
If so, that means even counting the psyker we've only seen four classes, and there could be another yet to be revealed. (The Vermintide games have five classes, so even if you're the fourth johnny-come-lately joining a group of three friends who've already called dibs, you've got two to choose between.)
Your class in Darktide apparently determines the available loadout options, with the example given of a psyker being able to wield a force sword but not a plasma gun. Each class also has its own special ability, with the veteran able to zoom in further and get bonus damage on headshots, and the zealot able to charge enemies, interrupting them and trapping them in melee.
While the classes are tweakable, it seems like they've still got personalities of their own, expressed through a complicated dialogue system. Edge quotes narrative director Mårten Stormdal as saying, "It's one of the most intricately implemented things we have in the game," and notes more than 75,000 lines have already been written for it.
Dialogue will be different based on whether a character is talking to someone they dislike, who they're standing near when they say it, and whether they're a rookie or have leveled-up enough to have seen some shit. Blessedly, the lines will also have cooldowns so you don't hear the same ones over and over.
Another detail from Edge's article that has made its way online is that the "storyline and missions will expand and develop after launch, almost as a live service." That's been interpreted by some as a full-blown Destiny 2 approach to campaigns, which I'd call a bit premature.
While it sounds like the range of mission types and certain lines of dialogue will be updated over the course of Darktide's life, it's too early to fret about a Destiny 2-style Content Vault where old parts of the game are retired so new players never get to experience them. It seems more like an additive approach, with updates making your missions into a continuing story rather than a campaign with a beginning and end you need to replay for the sake of character progression, as was the case with the Vermintide games.