John Wickhammer
 Psyker Build - Warhammer 40k: Darktide 

I've been asked a few times for my build so here it is. I wrote the guide below for friends that have not played gun psyker. It is helpful to know how the skills interact. This build is for auric and below. 

The auto pistol is not for shooting armor, use melee to deal with armor. Auto pistol requires you to get up close to the enemy. Generally you'll use melee in close quarters while dealing with specialists and gunners with a mix of ranged, assail and melee. This play style is aggressive as it requires you to be constantly killing to regen toughness and to maintain all your buffs through Disrupt Destiny and Malefic Momentum. Use Empathic Evasion to your advantage to ambush packs of gunners while being immune to their attacks.

Auto pistol allows you to run while shooting. It essentially has the run and gun blessing baked into it for free. I've seen people call the movement of auto pistol a gimmick but it is very powerful, allowing you to cover a lot of ground while doing good damage. Use the speed to your advantage and reposition if needed. I generally use it when moving between packs of enemies or chaining together kills marked from disrupt destiny. Auto pistol is slept on, but extremely fun if you work around its weaknesses! 

The Force Greatsword is very powerful and has easy combos. You should generally save a fully charged special for packs of armor or moments where the team getting overrun. I try not to use charged specials on pox walker hordes - use these to charge your special to use on bigger threats. It is situational, but having a charged special attack at the right moment can save the day. Since it has a built in stun, you can use it to stun enemies as well and to maintain high peril.

One of the most important parts of this build is always make sure your auto pistol has ammo and is not stuck on reload when you need it. It is crucial that you can pull it out at anytime to hit something for ranged immunity via Empathic Evasion! Crits also give toughness through Mettle, and Scrier's Gaze gives even more crits. Either way you are a crit machine. This is one of my favorite talents in the game as it can erase the threat of gunners as long as you have ammo. 

It's important to try and maintain high Disrupt Destiny stacks by killing the highlighted enemies. Killing the highlighted enemies also gives 25% toughness over 2.5 seconds, and often the game will chain these targets one right after the other as you're killing, so this is big toughness sustain (and big damage) as long as you're prioritizing targets. It is noticeable when Disrupt Destiny stacks are low, so try to maintain the stacks as high as possible and always try to seek out the highlighted targets.

Use Scrier's Gaze frequently. Don't feel the need to save it. Since the recent update and the ability to take Assail with Psykinetic's Aura, uptime on Scrier's is really good and there will rarely be a time where you don't have Scrier's available. Build Precognition stacks and maintain high peril, which benefits multiple skills. Extend Scrier's Gaze by quelling or shooting to utilize Tranquility Through Slaughter.

Warp Speed is really nice, if you fall behind for some reason or are out of position this allows you to get back into position very quickly. Plus it feels really good and is fun to move this fast. Use warp speed to close the gap with enemies, it makes for an aggressive play style. If this isn't your play style, you may want to drop Warp Speed for one of the toughness talents at the top of the tree.

Use melee for armor and non armor use mix of melee, assail and auto pistol. You should be somewhat rotating these 3 skills to maintain Malefic Momentum stacks and to keep peril high. Auto pistol offers extreme mobility, especially combined with the speed bosts from Warp Speed  Disrupt Destiny and Mettle. When you have these 3 speed boost buffs running you'll be faster than even knife zealots. This allows you to run all over the battle field, into the back line where the gunners are, and back to your team when armor is chasing you. Try to funnel enemies when doing this. Auto pistol quickly deletes packs of dreg ragers & maniacs. When scriers gaze ends and you're at 100 peril, unload all your assails. With 100% cleave from Warp Splitting, assail has insane horde clear and can even take out packs of scab ragers or maulers if all your buffs are rolling. There is a mod available that tells you how much time you have remaining for Warp Unbound.

Try to maintain high peril to get max buffs from Warp Rider , Warp Splitting , One with the Warp and Unstable Power. This is much easier to do now with the addition of Warp Ghost. Just a Dream is a really cool new talent, however you will be at critical peril a lot, so it may not work when you need it. I am skipping it for now. When you're at high peril, have Disrupt Destiny max stacks and Malefic Momentum and the rest of your buffs rolling, most stuff will die in one heavy attack to the head and you can chunk bosses. 

The only thing that feels "bad" with this build is not regaining any toughness after killing with assail or a group of enemies with the force greatsword special due to not taking Soulstealer, but this is easily worked around.

I don't take By Crack of Bone because it is too good at reducing peril. This build is better with high peril. I've tried swapping talents and find crack of bone to not really help this build as after playing with crack of bone extensively, stuff dies faster without it (longer at higher peril).

I've been using this build in auric expeditions and it is really good there. Speed boost from scriers is nice to have when running long distances and assail is really nice for wiping out groups of gunners on the move.

I was running this build with Inspiring Barrage for a long time and recently changed to Cavalcade. If you have trouble with losing toughness I recommend trying inspiring barrage, it can really save you in some instances as long as you remember it. Just pull out the gun at any point and shoot to regain toughness on demand. Cavalcade is a noticeable dps increase, but inspiring barrage is very usable and doesn't make the gun bad by any means.