Headpop Inferno - Making Brain Burst actually useful
 Psyker Build - Warhammer 40k: Darktide 

Thrive in any situation, and carry your randos to victory

This is a very generalist build that has no major holes or weaknesses, and can slot into any team composition easily, making it excellent for PUBs. It plays very similarly to how Psyker played before the talent tree overhaul, but without the frustration of trying to maintain pre-overhaul Warp Charges to do damage. 

BLITZ

This build is largely focused around making Brain Rupture a reliable, quick, and consistent tool for killing specials and elites, so this is the longest part of the guide. 

Empowered Psionics is absolutely key for this, cutting the cast time in half and cutting the peril cost to zero, making it far more spammable. The two upgrades, Overpowering Souls and Charged Up are also crucial: Having three stored charges of fast Brain Ruptures is critical for quickly killing high health Ogryns and Maulers, and getting a guaranteed charge of Psionics on killing Elites is easily the best way to build up charges, and also means you can pop Gunners, Shotgunners, and Ragers without spending a charge (provided you already have at least one). It also means getting a charge back on killing Maulers and Ogryns, effectively changing their cost from 2 empowered bursts to a net spending of only 1. You'll also be very effective in melee against these enemies as well, meaning easy charges. 

Kinetic Resonance (Combat Ability use makes Brain Rupture charge 75% faster and generate 50% less peril for 10 seconds) stacks with Empowered Psionics, giving you a lightning fast 1 second charge time compared to the base 2.5 seconds. It's a good way to get those first few stacks of Empowered Psionics, and also to dump all three stacks into a monster as fast as possible. 

• You can start a charge at 97% Peril and not explode. Just quell for a quarter of a second down from 100%, and you can keep charging without issue. 
• Empowered Psionics lets you hold a right-click Brain Burst charge indefinitely without generating peril: If you hear a disabler spawn and aren't drowning in hordes, pre-emptively charge the Brain Burst with right-click and detonate it on the disabler the split second they come into view. 

Brain Rupture Damnnation breakpoints are below.

RANGED (& SOULBLAZE IN GENERAL)

A well-built Purgatus staff is one of the strongest wave clearers in the game. Warp Flurry and Warp Nexus blessings make this thing basically play itself, and with a good Warp Resistance roll, Venting Shriek, and Battle Meditation (10% to quell 10% Peril on kill), the staff can often be firing more or less non-stop for a full minute. 

The quick attack has surprisingly excellent stagger, and is a good way to quickly stagger groups of shooters and let you close the distance to melee. 

To quickly explain Soulblaze and a few talent choices (namely the exclusion of Wildfire):

• Soulblaze deals damage over time, and without getting into the weeds of DoT calculation, deals exponentially more damage per stack: More Stacks = More Damage = More Better.
• Each applicator of Soulblaze has it's own cap for how many stacks it can apply per enemy: Wildfire can apply a max of 4 stacks on one enemy, Purgatus staff can apply up to 16, Venting Shriek can apply 31, and Perilous Combustion, 3. 
• Each applicator also has a cap for when it stops applying more stacks of Soulblaze: This cap is almost always the same number for it's application cap. This means a Purgatus staff can never take an enemy to more than 16 Soulblaze stacks, even if it has Soulblaze from other sources. If the number of stacks is lower than the applicator's cap, then they can still apply more stacks (for example, an enemy has 5 stacks of Soulblaze, a Purgatus staff could add more until the enemy reaches 16.).
• There is one exception to this: Perilous Combustion (Killing a Special or Elite applies 3 stacks of Soulblaze to nearby enemies) has a application cap of 3 but a maximum stack cap of 31, not 3. This means it will reliably add stacks in all situations.

Wildfire ends up mostly being a waste of a talent point, as 4 stacks is incredibly low, and can be applied just as fast with a Purgatus staff anyway. Also, try to use a high peril Venting Shriek on dangerous targets to apply max stacks of soulblaze instantly. 

MELEE

Your duelling sword fills the remaining gaps in your kit: It doesn't deal with crowds exceptionally, but the fire staff has that covered. The duelling sword instead gives you an excellent dodge, and superb single target, weakpoint, and critical damage, with a special attack that staggers anything on headshot. Using good melee fundamentals and defence, use the duelling sword to kill melee elites quickly, gaining Empowered Psionics stacks. With Uncanny Strike and Shred, it absolutely tears through armour. Shred's bonus to critical chance only goes away if you whiff an attack completely or attack with a different weapon: it's very easy to keep up. Combined with a number of crit chance and crit damage boosting talents, you can expect a crit chance of roughly 30% most of the time.

AURA, ABILITY, & OTHER TALENTS

Pushing cooldown reduction with Seer's Presence and other talents means we can use Venting Shriek incredibly often. Venting Shriek has huge range, huge stagger, and solid potential damage output due to Soulblaze, and tends to be useful in every situation. Use it more or less on cooldown whenever you need some space, an ally needs some space or is grabbed by a disabler, to continue vomiting out cyan flames like a firehose, etc etc. Tons of uses. Bear in mind that the higher your peril when used, the most stacks of Soulblaze it applies, ranging from 1 to 31.

Lastly, because we're going to spending almost all our time in melee or just outside of melee, excellent toughness regeneration is a must due to how squishy psykers can be, which is why every talent in the top quarter of the tree is taken. Combined with some toughness damage reduction, this should give you more than enough reliable survivability to very rarely if ever take meaningful damage while still playing very aggressively.

BRAIN RUPTURE BREAKPOINTS

* - Gives a charge of Empowered Psionics

SINGLE UNEMPOWERED BRAIN RUPTURE

• Scab Shotgunner*
• Dreg Shotgunner*
• Poxhound
• Sniper
• Scab Flamer*
• Dreg Flamer*
• Bomber
• Trapper
• Scab Gunner*
• Dreg Gunner*

SINGLE EMPOWERED BRAIN RUPTURE / TWO UNEMPOWERED BRAIN RUPTURES

• Scab Rager*
• Dreg Rager*

TWO EMPOWERED BRAIN RUPTURES

• Mutie (just barely, 1 nearly does it)
• Scab Mauler*
• Ogryn Reaper*
• Ogryn Bulwark*
• Ogryn Crusher*