PsyEmperor
 Psyker Build - Warhammer 40k: Darktide 

It uses lightning staff... but a lot of it is gonna just be left clicking and melee.

Force Great Sword (the mark you like) or any Force/OP melee weapon

Perks:

• Crit Chance -  a significant damage boost vs all enemies. Elite is solid, but only slightly more damage and only when Gaze/DD are not going. Maniac Lets you one shot head shot Mutants without other damage buffs but you should have damage buffs.
• Insert for most hated group here - Unyielding or Carapace are both very solid options here in Havocs.

Blessings

• Riposte - This weapon has some of the best crit multipliers in the game making crit chance actually good
• Shred - See the above. Unstable Power isn't good here because of By Crack of Bone, Warp Slice is fine though.

Surge - Perfect for long range single target removal, charges incredibly fast and quickly fills our peril gauge.

• Elite - For faster killing of all ranged elites and that are so annoying Maniac for specials or Unyielding are both good options
• Crit chance - More damage, more surge, more happiness 

Blessings:

• Warp Nexus - Way more consistent criticals, for more consistent damage - we are always going to have easy high peril on this build.
• Surge - more crit chance, and double hits when critting - left click SPAM 

With Gaze going you can have up to 55% Toughness Damage reduction which is quite good with how much toughness you can generate.

Use Sword special into elite swarms, or into hordes as a panic button to instantly recover your toughness.

Use Gaze regularly - it is a major component of this build, and only has an 11 second downtime when you factor in the lingering effects.
Assail  isn't really necessary, but I wouldn't want to use Smite in this build anyway. You can take Smite so you can get Psykinetics Aura, but it requires a more points so you have to give up some damage talents like Malefic Momentum or Toughness nodes and you should have impressive up time on Gaze regardless.