Dr Bees' Swarm of Bees
 Psyker Build - Warhammer 40k: Darktide 

Anything that I havent set are flexible slots for how you like to play the game. I encourage you to try things out and experiment with what you think are the best things to take.

This build is havoc 40 viable. It's one of the builds i crutched on to climb to 40. You have some insane dps output.

Explanations for the decisions I've made:

The knife:
This is a pure mobility knife. If you are hitting things with this knife, you are out of position. Run away and keep shooting. If they are point blank, and you have nowhere to run, push with the knife then just keep shooting. You'll deal more damage. The Stamina and Sprint efficiency perks are taken to supplement this playstyle of just using the knife as a mobility tool. I dumped first target, but it doesnt really matter as you should not be hitting anything with the knife anyways, just make sure you have 80 mobility, the normal melee dump stat.

Perks are Uncanny Strikes then whatever you want. You shouldnt be looking to make any effort to abuse uncanny, but its an extremely powerful global buff. This means that you can hit trash 5 times in the head to stack it up, then swap and inherit the 100% rending buff to your staff and heat procs. This interaction is omega overkill, even in havoc 40, but it does exist and would be disingenuous to not inform you of it. The situations where you *should* abuse it, however, are very very rare. Usually you can usually deal more damage by just spamming more shots on the staff and never pulling the knife out.

The Staff:
The star of the show, the bee launcher 5000. You spam left click with this and edge yourself at maximum peril, abusing the tap quell mechanic to shoot bees at an extremely fast rate. How many shots you can fire depends on your tree setup, but usually the three options are 3, 4, and 5 shots before you have to tap quell.
What is tap quelling? The game will show you on your peril number the number going down in a continuous manner as you hold down the quell button, but this is *not* how it actually works. The game actually quells your peril in discrete amounts in ticks that happen on a set interval. The number it shows by default is actually interpolated between the two discrete numbers in between ticks. This means that tapping quell for a single frame at 100% peril will immediately take you down to ~87.7% peril with how I have things setup, and you can immediately start shooting again without blowing your load. Remember: the only peril percentage that matters is the last one. So long as your peril isnt at 100%, you can do whatever peril generating thing you want without blowing up. even if its 99.9% you should not blow up. 

So the game plan with the staff is to shoot until 100% peril, then tap quell for a single frame. Then, depending on how your tree is setup, you count 3, 4, or 5 shots before you tap quell again, and simply loop the number of shots and tap quells. Don't lose count. This version is not as forgiving as the scriers version of the build that other people like to run. You are constantly edging yourself and making sure that you dont blow, which you can do indefinitely.

You may have noticed that I have opted to dump charge rate instead of warp resistance, and there is a very good reason for that. Warp resistance will determine how many shots you can get in before you have to tap quell. It can the difference between getting 3 shots between every quell and 4 shots between every quell, which over a long period of time is not an insignificant boost to your damage.

Speaking of dumping charge rate, you do not use the charge attack on this staff for damage. The damage and range are simply inferior, but it does have some niche utility uses. The charge attacks can open up bulwarks for you to shoot, and can stun chargers for a short amount of time. I also use it to sometimes kill spastic dogs that I cant hit because im washed and not actually that good at the game.

The perks: Carapace Unyelding
Pretty standard ranged weapon perks. You dont need flak because gunners, maulers, and ragers all just fall over to the bees. The only things that can survive the constant barrage you send their way for more than a couple seconds are crushers, bulwarks, and bosses. The boss damage on this build is respectable, but nothing amazing. Veteran, Scum, Zealot will all beat you in boss dps because of their burst potential. Its not bad, still shoot the boss, but you aren't melting it in seconds.

The blessings: Surge and Warp Nexus - Both mandatory
Surge: An utterly insane dps boost. You have ~60% crit chance with Warp nexus fully stacked up. You shooting out two shots (that both are crits btw) means that you are putting out about 60% more damage per second before accounting for critical damage bonuses. If you think about the crit it becomes even more insane, as since the extra surge shot is also guaranteed to be a crit, your crit rate is effectively ~75%, as that should be about the proportion of critical bees to non critical bees.

Warp nexus: Critical chance is insanely valuable, much more so on this build than it usually is on others. Its a mandatory pick on most staff builds, even the ones without the surge interactions. Insanely powerful blessing that will be at max power basically the entire game, with how you edge yourself to max peril every couple of shots.

The Curios:
Pretty standard perks/blessings. last slot is flexible. CDR is nice because you want to shriek as much as possible, though it too can be replaced if you want.

The Tree:

Mettle, Perfect timing: These are always active and always fully stacked up. your insane crit chance and fire rate guarantees it.
Soulstealer: Pretty good toughness regeneration, and you also need to take it to get to perilous combustion.
Perilous Combustion: The most busted node on the entire psyker tree. This is an effect that causes fire proliferation to enemies when an elite or special is killed. On higher difficulties with greater enemy density, this node becomes utterly insane witht he proliferation and proc chains that you can cause with this. Lets say you have a pack of 12 ragers, 8 maulers, and 4 crushers, which, all things considered, is a really small pack. You burn down the first rager, and now every single enemy in that pack has 3 stacks of fire on them. An okay amount of damage but not super noticeable. you kill a second rager and now every single one has 6 stacks. Noticeable amounts of damage, but not anything gamechanging. You kill a third and now everything has 9 stacks. Now it's starting to become alot of damage and will kill things on its own. 4 ragers might die to this fire, and suddenly, everything in the pack has 21 stacks which kills more ragers and maulers faster and suddenly the entire pack of ragers maulers and crushers have been deleted by the 30+ soulblaze stack positive feedback loop. Comically overpowered node.

You can take whatever blitz you want, since you'll never cast it manually. Brain burst is taken here because you can use the flex point to take kinetic flayer if you want, which is useful for bursting down crushers faster to start your perilous combustion chain reaction.

Lightning Speed: This, at first glance, appears to be a strange node to take. Why tf am i taking melee attack speed on my ranged only build. Well, the node is currently bugged. It effects all left click attack speeds, not just melee attack speeds. This includes but is not limited to: Inferno left click, Electro left click, Heavy Laspistol, voidstrike left clicks. Try it out in the psykanium. I guarantee you can feel the difference.

Souldrinker: Insane toughness regeneration. More crit chance always good.
Empyric Shock: This is always up. Free damage

Take whatever aura you want. I like to run CDR because shriek is pretty useful CC, but all of them are equally good.

Psykinetic's Aura: Mandatory node on all psyker builds. This is always up. Provides an insane amount of cooldown regeneration over the course of the game.

Empathic Evasion: Here is what the node actually means: So long as you are playing the game, you are immune to ranged attacks. 1 second is far more than enough time to get another crit, and so long as there are enemies to shoot, this node has 100% uptime. You can just go and stand out in the open against a firing line of hundreds of havoc 40 gunners and reapers and ignore all of them, blasting away at the laser lightshow.

One with the warp: You are always at max peril and thus always have 33% toughness damage reduction.

Shriek, Becalming Flames, and Creeping flames: Shriek has insane range (30m!) and because you should almost always be at max peril, you should apply 6 stacks of soulblaze to everything on your screen every time you press this. Its also some pretty useful cc for getting out of sticky situations. Additionally, this is your horde dps. This build struggles a small amount with horde clear, and you can shore up that weakness quite a bit with shriek.
Oh you can use this to stop yourself from blowing yourself up too i guess.

Vulnerable Minds and Warp rider: These two nodes are always taken on ever psyker build. Warprider is the node that makes up psyker's class indentity and core fantasy. You are always at max peril and thus always receive max benefit from this. Vulnerable minds is an insane damage buff on the targets you care about the most.

Solidity: Necessary to get more shots out between tap quells

5%tdr: travel and tax node.

Penetration of the soul: You struggle a bit with damage on carapace and this is a pretty noticeable increase in damage. You are always at max peril and thus always receive max benefit. This node is optional, however, and if you really wanted to fit something else on, I think that this might be the node to cut.

Warp siphon, Warp Battery, and In Fire Reborn: Damage and Cooldown. You really want the cooldown for shriek to spam it as much as you possibly can. Warp siphon helps with that. You take Warp battery for more charges which means more cooldown reduction. And you take in fire reborn because when you are fighting horde without a lot of elite and special enemies mixed in, your warp charge generation is kind of pathetic.

Now you may notice that I have left a point open. This is a flexible skill point that you can put in a few places to better fit your playstyle. Some notable choices are as follows:

Kinetic Flayer: As discussed earlier, Kinetic flayer can be nice to start perilous combustion chains faster.

peril resistance(-10% peril generation): Below and in between Vulnerable minds and warp rider. Taking this node will give you just enough peril resistance to eke out 4 shots between every quell rather than 3. Now, you may be wondering. Why not take battle meditation? Surely that node is just a straight upgrade right? Well, not necessarily. The reason why I dont take it is because it may be better, but it makes the build inconsistent. Battle meditation has a random chance to quell 10% peril. This will inconsistently fuck up how many shots you have in between quells, and the mental tax of "oh battle med quelled 10% extra peril, so i get two more shots" is not worth it. I much prefer to just count to 4 every time.

Empyric Resolve: This will allow you to shoot 5 shots between every shot before you have to quell at the cost of losing 30% of your toughness replenishment. Toughness replenishment affects all sources of toughness generation. Take this if you're a true gamer. I'm washed af though and like the extra tankiness.

Warp Ghost: +2 Stamina to run away more, and +25% toughness replenishment to make yourself much tankier. Very nice to have.

Nodes that I see other people take that I do not, though you could take if you really want:

Immaterial Focus: I do not take this node. Sure, this is up almost 100% of the time, getting stunned isnt so much of an issue as getting hit in melee in the first place. And the 10% dr is not that valuable, this build is already a little point starved.

Wildfire: I do not take this node. I dont believe it's necessary, as perilous combustion and venting shriek together is far more than enough soulblaze spread. It being capped at a gain of 4 is pretty sad as well. Nice to have, but I dont think I can fit this in the build.

Quietude: Nice to have. I cant fit it in.

Nodes that I think are traps:

Just a Dream: You are always at max peril. You will never benefit from this. Also: just dont get hit lol.

Battle Meditation (for this build specifically): See above in the peril resistance node explanation.