Wildfire Soulblaze & Aggressive Brain Burst
 Psyker Build - Warhammer 40k: Darktide 

Brain Burst

• With the power perks chosen (notably Warp Rider and Kinetic Resonance), Brain Burst will one-shot all specials and gunners. Adding Empowered Psionics, oneshoting Plasma Gunners, Ragers and Scab Ragers becomes possible.
• Kinetic Flayer can be triggered through various means :
  • any attack (range hits, melee hits and even the force push from the block follow-up of the force sword);
  • a brain burst attack (which means 2 brain bursts in one shot, notably one-shotting Mutants, Bulwarks and Maulers);
  • any tick of soulblaze damage on a valid target. This means that any soulblaze fire spreading is a good thing (ex: you brain burst a gunner, Perilous Combustion spreads fire to the gunner next to him which triggers Kinetic Flayer for a second kill).
• Empowered Psionics combined with Kinetic Resonance makes Brain Burst charge very fast. Adding Overpowering Souls enables to decimate groups of elites by spamming Brain Bursts after activating Venting Shriek (to trigger Kinetic Resonance).
• Use left click or right click appropriately:
  • use the left-click on far away targets or on targets that will leave your line of sight ( a running dog, an hiding gunner, etc.). Also use left click when you are alone or after triggering Kinetic Resonance. Spam it on Monstrosities.
  • use right-click charged burst when you are waiting for an enemy to exit its hiding spot or when you are not alone targeting an enemy (to prevent your burst from being cancelled because of the enemy dying prematurely).

Soulblaze

• Soulblaze stack sources:
  • Inferno staff attacks: 1 stack per hit, 2 stacks if the hit is critical;
  • Perilous Combustion will apply 3 stacks on enemies surrounding a killed elite or special;
  • Wildfire will spread stacks from enemies with high stacks of soulblaze. At least one stack will always be spread;
  • Creeping Flames will apply 1-6 stacks (based on the peril level) to enemies in a cone in front of the player. At 84+ peril, 6 stacks are applied (you ideally always want to be at this peril level when using Venting Shriek ).
• Soulblaze damage is exponential: 4 and less stacks does very little, 5-8 stacks will clear hordes easily and 10+ stacks will decimate elites (except Crushers). 
• Max number of stacks with the staff is 15 stacks (possibly 16 if the last attack crits). Creeping Flames can reliably push that number to 21-22 and with additional triggers of Perilous Combustion the limit of 31 stacks can be reached.
• Stacks will start to quickly decay after a while (around 10 seconds). Reapplying at least one stack will reset the decay timer.

Knowing all this, the main strategy is as follow: apply as much stacks as possible with the inferno staff, then focus elites and specials to apply additional stacks with Perilous Combustion. Use Venting Shriek when you need to quickly apply a lot of stacks to a large group of enemies. For monstrosities, reach the stack limit as soon as possible then reapply a stack from time to time to keep the total number of stacks high, otherwise switch to your melee weapon or brain burst for damage while the soulblaze fire does its job.

Peril

• Peril level should remain high as it provides damage with Warp Rider and defense with One with the Warp. 
• When switching to the force blade, Unstable Power will provide up to +20% power (4 stacks of +5% power) which will benefits to the Soulblaze damage being done to enemies as well as its own damage.
• Peril level is easy to manage with the staff as it builds up slowly. As long as you start a charged attack before 100% peril, you can perform the full attack without overloading.

Defense

• The Inferno staff is also useful for its high crowd control ability. The Terrifying Barrage perk will help stop lesser enemies in their track when spamming charged attacks, while elite enemies (maulers and ragers) and specials can be staggered by single attacks. Warp Flurry helps with charged attack spam.
• The Deimos force sword is used as a more defensive option compared to the duelling sword. Kinetic Deflection combined with Deflector allows to block both ranged and melee attacks with peril before stamina. If your peril gets high by blocking and your stamina then breaks, Immaterial Focus might save you. The push follow-up attack is also a great tool to repel Poxbursters or stagger any elite/special.
• Quietude (through Quelling peril with Venting Shriek), Souldrinker, Warp Ghost and Psychic Leeching will help generate toughness.