Flame Shriek Havok 40 Psyker
 Psyker Build - Warhammer 40k: Darktide 

The non-bubble'd Flame Psyker.  Classic flame psyker, you paint the screen blue until you stop seeing heretics. 

Choices- I opted for Mind in Motion exclusively for that 5% movement speed. Combine this with the 5% mettle movement speed on crit, and you are moving at a pretty noticable increase, as this build should have you critting near constantly, so long as there are enemies in range on screen. 

I dont bother with the Vulnerable Minds 20% increased damage to Ogryn and Monstrosities. Thats a trap pick for a Flame Psyker. Your job is to empty the screen of everything except for the big guys, so your Hammer Zealots, Plasma Veterans, etc, arent having to play wade through the pox walkers to target the things they want to target.

Warp Ghost and Kinetic Deflection are must takes for survivability/mobility. Warp Ghost is a major boost to your low stamina, and the toughness replenishment is extremely nice. the -80% Passive Quell is take or leave, but it helps in keeping that peril in that sweet spot between blasts of Venting Shriek. 

GAMEPLAY LOOP- You are wanting to do an initial large sweep of the flame-paint of approaching targets, then use small blasts of primary fire to stagger the enemy back. Rinse repeat until at the point your brain will explode, then exhale a Shriek into the largest clump of hostiles on screen available. Keeping your Warp Siphon stacks at 6 will help keep this cycle quick, with extremely fast up times. Between this ability and your flame staff, you can more or less instantly remove most enemy hordes, leaving only the largest elites behind to then get bullied by your team. You are aiming to get your enemies to 10+ soulflame stacks on them at any given point in time, and ideally getting them to 15 stacks before unleashing a Venting Shriek on them. If they are anywhere between 10-15 stacks by the time the Shriek hits and adds another 6 more, those enemies will only exist for a little while longer. 

Your sword is your defense weapon, with venting Shriek and Kinetic Deflection, you can block all day, mixing in a few ripostes to defend yourself from overheads. You are only breaking this out to Heavy Attack Specials that get in your face, or assist with Boss damage. The vast majority of your time should be with your flame stick paintbrush out, turning the battlefield blue. 

The single biggest way you can get yourself killed is being in front of your team. You are to hang in the middle/back of the squad, crisping the hordes that appear to the front and back of you. What you want to focus on most is positioning, ensuring you are not stuck in a corner with no escape, blasting fire in all directions while the enemy collapses in on you. You can Shriek into a Kinetic Deflection defensive posture, but ideally, you are not putting yourself into a position where you need to be rescued. Ideally your Shriek will give you space to reposition. 

Alternative options- if you feel that you dont need to have that extra 5% movement speed at all times, swapping Mind in Motion to Channeled Force can squeeze some extra damage out of your staff, but I personally feel this is too little for too large an investment with the options. Most of your psionic damage will be from your flamestacks. 

Immaterial Focus's 10% damage resistance is VERY good, as is being Stun Immune, but your utility from that is limited. Far more noticable a must take for melee-psyker. 

Perilous Combustion is still goated despite the Depths of the Damned Nerf. That little bit of extra push on flame stacks does matter for getting the critical mass built up. 

If you are struggling to balance Perils of the Warp and popping your brains periodically, I'd suggest taking an Extra Wound Curio until you learn not to do that. You should be actively CHOOSING to place yourself into brain-pop territory because of your desire to maximize flame stacks out of Shriek, not because you thought you could squeeze another blast of fire before you needed to Quell. You want to Quell down to about 60% when you start seeing the upper 80's 90's with your peril. If your hearing the rush of the warp in your ears, its already too high. Stop embarassing us Psykers collectively, and learn to eyeball that Perils counter. 

Considering you also are not running Bubble- Swapping Toughness % on your curios for Gunner Resistance to some extent may be worth consideration. Thankfully Gunners are extremely easy to suppress with Flames, and sliding is your friend for avoiding getting turned into swiss cheese.