The Callidus - Scum Assassin Build
 Hive Scum Build - Warhammer 40k: Darktide 

A Lightning-fast Crit Assassin Build - "To assume the shape of the accursed and deliver death from the purity within you - that is to be Callidus."

"To assume the shape of the accursed and deliver death from the purity within you - that is to be Callidus."

• The Shapeshifter's Axe (or simply the tac) - A great crit-based all-rounder. Get an auto-clicker and aim for the head, and you will be just fine. The Sweet Spot while in an Adrenaline Frenzy creates a perfect storm of precision violence. Brutal Momentum may seem tempting, but I find the extra crits provided by Shred to have greater utility, and cleave is not super useful on the tac. Unless you are a Pro, Street Tough has a good uptime for speed and keeping you safe; recommend for any hive melee build! 
• Rampage - Your combat stimulant, the synthetic equivalent of the polymorphine that allows your brethren to change their form.  Adrenaline Smiter has by far the best uptime into auric and above. Its raw damage sends your crits skyrocketing. While Forge's Bellow provides a momentary distortion to allow you to slip away or go for the kill.
• The Thanatek's Sting or Needle pistol - Allows you to contribute effectively vs bosses and armour, while Pickpocket is an option, a true Callidus assassin need not resort to such crude methods when precision and patience suffice. Run 'n' Gun keeps your shots accurate when on the move and Stripped Down keeps you safe when approaching a group of gunners.
• Polymorphine-7 Stim - Not yet the shapechanging elixir yet, simply here to make the weak-spot hits even better through its finesse damage. Remember the Callidus creed: always aim for the head!