Relic Fanatique ( Havoc 40 )
 Zealot Build - Warhammer 40k: Darktide 

Build Alternatives :

1. If you are in need of Corruption cleanse, replace Benediction with Beacon of Purity. This will remove one of the most important part of your tankiness which will ask for some adaptation, in exchange you will give to your team a much needed cleanse.
2. If you feel that your tankiness isn't enough, then swap Punish Impiety for Shield of Contempt. You will lose an non negligable ammount of damage in exchange for better team wide survivability.
3. If you want to play more into the staggering ability of the Munitorum Mk X Relic Blade, swap Desperationfor Punishment. 
4. You can swap Heatsink for Energy Leakage on your Munitorum Mk X Relic Blade if you desire more damage during your special mode uptime rather than longer usage of your special mode.

Strength :

• You are an exellent horde clearer. Between the raw stagger and cleave ability of the Munitorum Mk X Relic Blade and your secondary option of burning everything to the ground with Artemia Mk III Purgation Flamer. Be it flontlining to give your team space, or taking care of a secondary wave that come from the back, you will be able to handle both on your own. If your team doesn't have a psyker or a primary horde clearer, you will be able to do the job very strongly as long as you keep the ammo sustained troughout !
• The same staggering ability that is used against hordes have the same effect against priority targets like Crusher or Scab Mauler, paired with high heavy attack damage and decent penetration even outside of Fury of the Faithful, you will be able to deal with any armored targets, elites and specials without any issue. ( outside of Rotten Armour ! )
• Fury of the Faithful will provide you with many options. An escape tool if you are ever in need of one, a good way to regenerate toughness, a heavy stagger against Crusher mid overhead ( be it for you or a teammate ), great movement to quickly close the gap against gunners and finally, exellent damage against any target in the game with the 100% rending + crit chance and 25% melee damage. Its Cooldown also being very low due to Martyr's Purpose, Redoubled Zeal and Fury of the Faithful, maintaining a magnificent uptime troughout a game.
• Munitorum Mk X Relic Blade damage is directly related to how much you can boost it's attack speed. Between the 10% of Punish Impiety, 25% from for 10s on Fury of the Faithful use, 30% at max stacks of Martyrdom due to Maniac and the 10% from Faithful Frenzy, you will be able to constantly dish out a very high ammount of damage while maintaining good fight agility for a slower weapon.
• Benediction will provide you and your team a very nice boost of survivability.
• Until Death and Holy Revenant will allow you to stay alive while being much more aggressive and keeping high Martyrdom stacks. Meanwhile Fury of the Faithful 50% toughness regen + the follow up guaranteed crit procing Enduring Faith and generally Prime Target + Second Wind constant uptime during fights + Benediction, I Shall Not Fall and Toughness Damage Reduction 10% will keep your toughness high.
• Blades of Faith will allow you both quick switching towards your Artemia Mk III Purgation Flamer( necessary when both weapons are slow to begin with ) and picking off disablers or easy to kill elites at a moment notice.
• Providence and 3 Revive speed curios give you the ability to raise up allies extremely fast.

Weakness :

• You do not possess any long range options. Ether you hit marvelous Blades of Faith throws, you close the gap with Fury of the Faithful ( but be aware of where your team is ! ) or you rely on your team to do the long range fighting. As you aren't using Blazing Piety, all secondary crit weapon that a zealot could use become unreliable. You might be tempted to use the Godwyn-Branx Mk VI Bolt Pistol but your impact will be lessened significantly.
• You do not have enough raw piercing armor damage to handle Rotten Armour spam as it is. You will do damage, but too slowly to make an entire boosted Crusher pack go down before being put into a disadvantageous position.
• You will do good damage against bosses, great damage in fact with Fury of the Faithful crit weakspot hits, but not only do you have to position yourself to actually have the weakspot hits, you also have to be careful around Scab Captain. What do i mean ? you say, well, captain pushbacks will cancel your Munitorum Mk X Relic Blade special ability, forcing you to reactivate it before launching your attack. Also, if you aren't fighting Twins, you will need your team to down the shield and let you sprint + Fury of the Faithful heavy attack the boss just like a Crucis Mk II Thunder Hammer build. otherwise, you will loose a lot of damage for that boss. 
• Munitorum Mk X Relic Blade is one of the more complicated weapons to understand and use in the game. Possessing a lot of different paterns and variation, the learning curve is steeper and the skill ceiling higher. Basically, more involvment for higher rewards, but harder to master.
• You aren't a Chorus of Spiritual Fortitude zealot which means you provide less stagger and no golden toughness for your team in exchange for that raw damage. That will make your team comp change significantly. It also might be harder to be taken ( or kept ) in groups of randoms rather than a team you know.
• You won't create the space an ogryn or Chorus of Spiritual Fortitude zealot provides while still occupying a fronline slot. 

Special Info :

Considering the difficulty to master the Munitorum Mk X Relic Blade, here are a few advanced tips:

• You can chain Heavy overhead without going back to heavy laterals by ether doing a quick attack after 2 heavy overheads or a very fast block animation canceled back into overheads.
• Lateral Heavies aren't as good as light attack spamms for horde clear.
• The sprint heavy is the most armor penetrating move of this weapon. You do not have to wait for the weapon to be fully down to be considered a sprint heavy. As soon as you see it slightly lower itself after you start sprinting, it'll be considered a heavy sprint attack. Keep in mind that you cannot do a sprint attack while being in the middle of your usual combos, you have to stop your combo, gain some distance, start sprinting and see your Munitorum Mk X Relic Blade go slightly down to use it properly. ( It will reset the 2 heavy overheads ! ). This sprint attack is great to engage any fight with, to be used in correlation with Fury of the Faithful, or to be used specifically against Crusher, Twins and Monstrosities. ( 2 overhead heavies, backing off slightly, sprinting and sprint attack heavy )
• Light attack spam against Scab Captain shields is the way to go, in fact, they do not need to be under your special enchancement for them to be effective, as you will almost do the exact same damage to the shield.
• Letting your weapon overheat without having Overload blessing equiped is terrible, it'll be much slower to get back your special ( the 25% reduction from Overload being exactly the time increase without on lockout ). When you are getting close to lockout, ether quick swap to your Artemia Mk III Purgation Flamer with the Blades of Faith cancel animation ( the fastest way to get out of your special ) or use the special again to cancel. 
• Your special activation and deactivation also count as a block ! ( you won't block a Crusher or Scab Mauler overhead ! ) which can be used to ether block in tighter situation or activate Counterattack if blessed with. The window of block is very small and won't block more than one attack at a time so be careful of the usage of this ability.

The rest is basically learning ! When to swap from one combo to another ? How to swap seemlessly from one combo to another ? How to position yourself to be the most effective ? When to use the sprint attack ? 
The smoother you use the weapon and the better you understand its usage, the stronger this weapon will become !

Conclusion :

Not meta ! ( obviously, if you're starting to know me from reading other guides of mine ;) ) But strong without question ! Even so too limited to be used in Rotten Armour without a team that supports it, will work without any issue in Havoc 40. 
Longer to learn and quite a few things to keep in mind as you play, Yet very fun to use and play around with ;) 
Not as much Alternatives as the other ones i made so far, what can i say ahaha. 

Worth every min i gave to creating it and using it ahaha ;) hope it'll be the same for you ;)

I encourage you to try it out and tell me what you think ! ;) ( Giselle5957 on discord ;) )