Mortar and Pestle
 Zealot Build - Warhammer 40k: Darktide 

Stagger armored hordes with Crusher and assassinate Elites and Monstrosities with Throwing Knives and Double-Barreled shotgun + Shroudfield* and Manstopper blessing.

*Non-Master-Crafted for reduced teammate aggro dump.

The loop:

• Use Crusher special into armored hordes to control space and apply stagger/debuffs
• Use Crusher push attacks to kill elites and specials and to replenish throwing knives
• Use Shotgun for gunner suppression and in tandem with throwing knives for elite/specialist kills
• Use Shroudfield with throwing knives and shotgun for boss assassinations
• Use Shroudfield ability and Scattershot blessing to proc Manstopper blessing with throwing knives and shotgun for infinite cleave into non-Carapace armored enemies.

Notes:

• Master-Crafted Shroudfield: Avoided so as to prevent extreme aggro-dump to teammates. Less time in stealth and not having 5s of -75 threat means that enemies will reaggro the Zealot quickly after Shroudfield use. With Master-Crafted Shroudfield, the max duration of the aggro dump is 10s, without it is only 3s. This will reduce shroudfield activation success rate overall as well as losing the additional melee backstab damage but it will also mitigate cascading team wipe situations which are often caused by Master-Crafted Shroudfield.
• Bosses:
  • Backstab/Flanking
    • For optimal high damage against melee captain and Rinda Karnak, apply brittleness with Crusher and use Shroudfield and Crusher Weapon Special Heavy (or Push Attack) backstab.
    • For optimal high damage against ranged captain and Rodin Karnak, apply brittleness with Crusher and use Shroudfield and fire shotgun double barreled shot.
    • For all other bosses, apply brittleness with Crusher, activate Shroudfield behind boss and immediately throw 1 knife followed by double-barreled shotgun shot.
      • Plague Ogryn, Chaos Spawn, and Beast of Nurgle bosses allow for high damage weakspot flanking hit shotgun assassinations if having favorable positioning.
      • Use Full Bore blessing instead of Scattershot if additional boss damage is preferred.
  • Counterattack
    • When having boss aggro, wait for boss or other enemy to attack and dodge to proc Duelist before activating Shroudfield for throwing knife / shotgun combo into weakspots. Effective against Beast of Nurgle, Plague Ogryn, and Chaos Spawn.
• Survivability: The combination of Enemies Within, Enemies Without, Second Wind, Until Death, Holy Revenant, Good Balance, and Enduring Faith in tandem with Shroudfield+Invigorating Revelation will have good all-around survivability but these can be adjusted somewhat based on preference, team build synergies, and skill level.

Since the patch nerfed Shroudfield to only permit 1 throwing knife to be thrown during the activation grace period, the effectiveness of both boss damage and manstopper cleave utility against hordes/elites is reduced. This setup with full bore instead of flechette will retain significant boss damage while still providing high stagger, debuff, and cc value for your team.