The Psy Assassin - Stab and Smite Build
 Psyker Build - Warhammer 40k: Darktide 

Psy-Assassin Smite Build - "Besides, who better to hunt a witch than a Psyker?"

Whats a Psy-Assassin you asking? , are you saying you don't know niche lore from 40ks glory Days of 1988?! 

• The Psy Blade (Catachan Mk VI Combat Blade) - The high mobility and stout defense keep the assassin safe from the horde, and both pair well with the large number of crits you’ll be getting. With Flesh Tearer and Uncanny Strike, It becomes an instrument that slips between the plates of the larger armoured beasts. Heavy spam is mainly the aim of the game here with the occasional push-stab into specialists. Charged Strike is actually boosted by Empowered Psionics so is very synergistic with the knife.
• The Hollow Stance (Scrier's Gaze) - Your Deadly combat stance, quick with Warp Speed and to turn your blade into a tool of death and mayhem. The Gaze also gives you the tool to do  maximum smite damage thanks to Warp Unbound. 
• Synaptic Storm (Smite) -  Use it in two situations only. First, when you’re at max peril thanks to Scrier's Gaze , for busted horde clear and to take the pressure off the team. Second, to cover revives or objectives. You only have one charge with no Charged Up, but if you need more than one, you’re simply smiting too often. A trained assassin doesn’t throw power around. He spends it once, in the right place.
• Secondary Sanction Pistol (Accatran MG Mk II Heavy Laspistol) - Perfect for gunners and particularly Monstrosities due to Infernus stacking. This is a reserve weapon on this build but its high finesse stats mean it plays well with Scrier's Gaze is facing a boss at range. A professional keeps a backup for the targets the knife can’t reach.