Sicarian Infiltrator
 Zealot Build - Warhammer 40k: Darktide 

Sure. We got Skitarii now. But can skits go invisible? Didn't think so.

Munitorum Mk II Relic Blade: Chunk bosses (or oneshot with combat stim) with running attack weakspot backstab (oneshots are for funsies and require more melee dmg talents). Clear mixed hordes with push attack light repeat, and fight carapace with light light (heavy) repeat or (light heavy) repeat (heavies use charge more efficiently, lights faster dps). Always use running attack with shroudfield when killing bosses, practice hitting their weakspot from behind. Don't empower your relic blade for light hordes, you just don't need it with Wrath + Rampage. Save it for mixed hordes or metal balls of death, or full density. Always go for headshots, look up for nasty damage uppercut headshots. It's more forgiving than you'd think letting you get the headshot. Activating the relic blade is twice as fast if you are sprinting. If you're coming off a strange swing combo or default activation animation, blocking then sprinting is a consistent way to quickly get into the running attack instead of fumbling around waiting for your character to point the sword in the right direction. 

Accatran Mk XII Recon Lasgun: Makes you immune to ranged enemies, super fast, and deletes snipers/specials quickly with headshots. Don't use it to fight gunners, use it to close the gap against them. The las shots are for specials and snipers only, or when there are too many reapers to melee. Pump a few shots into bosses to set them on fire before going in for the oneshot; it takes just 15 shots on average (like half a second) to get full burn stacks, and that can help you get the boss oneshot refund from Perfectionist. Or just blast the boss, run away and kite, repeat til you're ready to fight it. 

What is a Sicarian Infiltrator? They are Skitarii of the Mechanicus that specialize in infiltration and disruption. They blast deafening white noise and fry local electronics not blessed by the machine god. They were Skitarii forces ripped apart or mutilated at the end of battles, barely alive, deemed worthy enough to be remade by steel. They are armed with power weapons, stub-carbines and flechette blasters (light small arms fire), and have stealth fields that make them take less damage from enemy fire. On the tabletop they are used mainly to do battlefield objectives or deepstrike into the backline to skirmish or screen against key targets, having stratagems to get them out of sticky situations. Their close equivalent (same models different headpiece), the Ruststalkers, specialize in picking out the opponent's HQ's and leaders in melee and killing them quickly before you usually would be able to (characters are usually protected until you clear the infantry around them).

In game, this build is barely alive (Martyrdom) and specializes in infiltration of the backline (Master-Crafted Shroudfield +  Thy Wrath be Swift + Stripped Down) and eliminating key targets (Shroudfield). It's armed with a power weapon (Munitorum Mk X Relic Blade) and an assault rifle (Accatran Mk XII Recon Lasgun), protected from enemy ranged fire (Stripped Down + Wait in Line) and is able to do objectives or revive where others can't (Shroudfield). You can deal massive damage or oneshot bosses and key dangerous enemies while not having to worry about the horde around you, and always have a get out of jail free card in your back pocket.

Martyrdom: Martyrdom is an interesting ability for one reason: it makes all melee dmg and attack speed talents/nodes worse. Going from 100% to 115% attack is much more impactful than going from 150% to 165%. This especially applies to attack speed, and the difference between having nodes like Faithful Frenzy and Punish Impiety and not having them is negligible, because you're starting at 130% attack speed and adding 10% to it instead of starting at 100%. You don't need more attack speed. It also makes all damage reduction nodes better, since they all multiply together and make each other stronger. This is clear if you consider the reciprocals instead of the resistances, you're stacking 1.25x, 1.33x, 1.15x health and toughness multipliers on top of each other and every one you get makes the absolute value of your EHP increase more and more efficiently every time you get another one. Not to mention the toughness replenishment buff on top of it all. Talents like Shield of Contempt The Master's Retribution Retaliatory Defence Zealous Pilgrim On the Brink and Risen can be taken since Martyrdom gives you enough damage already. Invigorating Revelation isn't taken because it overlaps with the 4 seconds of unkillable and following 5 seconds of gold toughness; you just don't need more damage resistance during that. 

Fucking booking it: If your whole team goes down, kite until Shroudfield is up and your teammates are waiting to get rescued. You're probably surrounded on all sides. Pull out your lasgun, pop your ability, and with an 80% movement recon lasgun + Master-Crafted Shroudfield movespeed you will no longer be surrounded by enemies. This all but guarantees getting to the rescue point. Then kite again until you have another shroudfield (preferably killing some ogryn enemy to get 9 seconds off your cd) to start picking up your team. This is reliable and saves games. I essentially use the lasgun like a knife in cs, a sprint/movespeed boost to get where I need to go quickly, even pulling it out between sword swings to close gaps. With Stripped Down and gunner resist, the most threatening enemies in the game are truly no big threat to you. Stripped Down interacts with dodge talents like Second Wind and Good Balance, meaning enemy shots heal you. You can also use Zealous aura to make the invincibility even better!

Curio Perks: Ability cooldown is fake with an opportunistic ability like Shroudfield, especially if you take Perfectionist. It is not a DPS-ing ability, you will have it available quite often and it's not optimal to just spam it. If you don't use your ability within 3.6/1.5 = 2.4 fucking seconds of it coming up, you're throwing away 3 curio perks. Instead, this setup has 2x gunner resist (1 curio 1 talent), 2x stamina regen, 2x ally revive speed, and 2x block cost reduction (1 curio and Zealous). Since we run Master-Crafted Shroudfield, the 2x ally revive speed can be exchanged for anything you desire, but it's nice to have. Taking 3 block cost reductions alongside Zealous can let you do very, very funny things especially alongside Retaliatory Defence. In fact it can entirely replace using Shroudfield to revive at all as long as you aren't taking ranged damage. Alternatively go 3x toughness, stamina regen, gunner resist. Keep it simple, keep it strong. 

Blades of Faith are mandatory these days TBH. You should NEVER pick up nades, ever. If you use nades, it's 3 per mission. They lack the clutch power of Stunstorm Grenade or Immolation Grenade, but are quick and reliable special killing at medium range and help keep you in a melee flow state. Whenever I use stunstorms I feel like they do literally nothing, as the stunned enemies are immediately replaced by the rest of the horde behind them. Immolation Grenade is great for throwing down at big groups to eliminate the chaff or to secure your surroundings while you revive a teammate, but scum's Chem Grenade shows just how powercrept zealot's are. They're better on Chorus of Spiritual Fortitude builds since you can use them to heal with Holy Revenant.