Melee DoT Psyker
 Psyker Build - Warhammer 40k: Darktide 

This is a Psyker build that basically plays like a Zealot. You're trading Zealot's throwing knives and general tankiness for insane movement speed and an extra damage-over-time effect on your heavy attacks with Charged Strike. Combined with bleeding from Flesh Tearer and burning from Infernus, electrocution gives you a 3rd DoT effect and all of them will be scaled by Uncanny Strike and the various damage buffs in the build. Be warned that this build relies more on player skill for its survival compared to a typical Zealot build, so it can die easily if you make mistakes with dodging, blocking, positioning, etc. It's fun and rewarding to play if you can pull it off.

Perilous Combustion gives situational access to a 4th DoT effect from specialist/elite kills. Soulblaze needs 6+ stacks to deal significant damage, so this is mostly relevant to fighting elite blobs on Auric/Havoc. It can help quite a bit for clearing out armored packs and mixed hordes after the soulblaze stacks get rolling though, especially if you have another soulblaze Psyker on the team.

Malefic Momentum will gain "warp attack" charges when enemies die from either electrocution or soulblaze, and "non-warp attack" charges from your direct damage or bleeding/burning, so you can easily gain both kinds of charges as long as you let some enemies die from DoT and some from direct damage.

After trying a few different options, I think the Mk VI knife is the best melee weapon for this build because it has access to both bleeding and Uncanny Strike, it has cleaving heavy attacks, and it has great mobility. The horizontal cleaving heavies on the Mk VI knife are also effective at getting multiple weakspot kills for By Crack of Bone, enabling higher Scrier's Gaze uptime during hordes. Illisi force sword (with Uncanny Strike + Riposte blessings) is also a good option, but compared to the knife it loses bleeding, has worse mobility, and you most likely want Warp Unbound to avoid blowing yourself up during Scrier's Gaze. While the force greatsword might seem like an obvious pick for melee Psyker, this build wants cleaving heavy attacks to apply Charged Strike and the FGS has single-target heavy attacks, and also lacks access to Uncanny Strike. Devil's Claw and heavy swords have good cleaving heavies, but they lack access to both Uncanny Strike and bleeding.

Ranged weapon is mostly down to personal preference. You want a gun that has fast swap speed for quickly killing specialists when you're already engaged in melee. I like the Mk II laspistol because it has increased base crit chance for more Empathic Evasion and Infernus procs, good accuracy for long-range targets, and good damage vs unyielding for killing reapers and bosses. Most builds will take Dum Dum as the second blessing, but I like Desperado on this build because with +20% crit chance from Scrier's Gaze and +20% from the blessing, you can be practically immune to ranged attacks with Empathic Evasion even while having a shootout with a room full of gunners. Recon lasgun, bolt pistol, and Zarona revolver are also good options, but they all have tradeoffs compared to the laspistol.

On the laspistol, you can take either damage vs flak or unyielding. Flak will be better for killing elite gunners, while unyielding is better against reapers and bosses/monstrosities. You want +5% crit chance perk for sure since this weapon gets huge crit damage scaling and it also helps proc Infernus and your crit talents more often.

The build does also have Smite if you're inclined to use it. I almost never use Smite myself because I just dislike it, but this build can easily transition from melee berserker to crowd-control support when needed.

You can choose either Prescience or Seer's Presence for your aura. Prescience is more useful to yourself and Seer's Presence is probably more useful to your team. Use whichever you prefer, or whichever the other Psyker on your team isn't using. For PC players, consider using this mod to easily swap auras without having to recreate your entire skill tree: https://www.nexusmods.com/warhammer40kdarktide/mods/216

Lingering Influence can be swapped for Just a Dream for more survivability at the cost of lower DD uptime. Mettle could also be swapped at the cost of movement speed and toughness recovery.

If you're playing on a difficulty below Auric, Perilous Combustion probably doesn't provide enough value to be worth taking. You could replace it with Tranquility Through Slaughter for higher uptime on Scrier's Gaze while shooting, but I would only recommend that if you're using a gun with high rate-of-fire, such as laspistol or recon lasgun. If you use a gun with slower reload speed like the revolver, then Surety of Arms is a good choice. Otherwise, Lingering Influence is good for increased uptime on Disrupt Destiny.