As players who will visit this guide probably know - Grim Dawn is a game of choice and consequence and that's a reason it is so loveable. This is one of the basic RPG features - you decide to do something and whatever happens afterwards is because of you, because you chose to do it and you have to go through with it.
But anybody knows that sometimes you make a choice and are absolutetly not satisfied with it.
Now it's not that big of a problem in Grim Dawn but since the decision between the Order of Death's Vigil and Kymon's Chosen is something that can influence the direction you will take in the game quite a bit, I decided to make this guide.
More precisely I will focus on the item-side of the two factions, I will say a few things about their lore, getting reputation and bounties but the main focus will lie on the equipment you can get out of them.

So now I'm here, but what is this all about? I play the game but I have never heard of these factions you mentioned, even less so of this quest?

After you arrive in Homestead and help out there for a bit, your good friend and not-so-much-cook Ulgrim will introduce two strange fellows to you. Well more like they will introduce themselves to you and then you stand before the choice which believer to follow.
Afterwards you will be stuck with either faction and the other one will hate not love you, for your decision.

However fear not, if you already made a choice and find yourself in the situation, that you don't like the faction you took. It is possible to revert your choice on higher difficulties, however your reputation/infamy with both factions will reset on changing them!

Please mind a few things while reading the guide:

1. Please check the Changelog to see which part of the guide is up to date to which patch/build, I always try to have it all at the same level but I don't always do so in the end.
   
2. Item stats change everytime you visit the vendor - neither did I wait for high values nor low values, I just took the items I got.
   
3. Item skills scale with player bonuses and this is also shown in the tooltip - I did take Screenshots without any equipment but due to skills and attributes I still couldn't get 'normal' values.
   
4. If however, the stats differ too much, please give me a heads-up - I will have a look into it.
   
5. You can probably find the latest stats over at Graceful Dusk[gracefuldusk.appspot.com]

Work in Progress.

If you chose to side with the charasmatic man by the name of Brother Molltair, you decided to follow a man called Thaidrus Kymon - a self proclaimed prophet. A man who's quite litterally gone through fire... more than once.
Additionally every evil follower of the Order of Death's Vigil will forthon be your foe for life, just as every Chtonic creature roaming the world of Cairn.

You will gain reputation by:
+ Killing Chthonians
+ Killing Order of Death's Vigil
+ Quests
+ Bounties

Primary equipment bonuses are:
+ Fire Damage
+ Lightning Damage

+ Fire Resistance
+ Lightning Resistance
+ Vitality/Chaos Resistance

All prices are with Revered Reputation.

Work[grimdawn.wikia.com] in Progress.

If on the other hand, the mysteriously looking Haruuv manages to aquire you for his cause, you are now following the one called Uroboruuk. A man betrayed by his kin, and tortured just to not be able to die. Just as him you will journey around to learn about the mysteries of life and death.
Moreover you will fight against the heretic Kymon's Chosen and the possessed Aetherials.

You will gain reputation by:
+ Killing Aetherials
+ Killing Kymon's Chosen
+ Quests
+ Bounties

Primary equipment bonuses are:
+ Cold Damage
+ Vitality Damage
+ Pet Damage

+ Cold Resistance
+ Vitality Resistance
+ Lightning/Aether Resistance

Prices are with varying reputations.

Work[grimdawn.wikia.com] in Progress.

Since Build 28 every faction has some Component Blueprints to sell and they won't drop off of monsters anymore.
These are the same for both factions, meaning if you chose the Order of Death's Vigil or Kymons Chosen will have no effect on the Blueprints (for Components, mind you), you will get.

All prices are with Revered Reputation.

For Information and help on the Bounties, check out the wiki-pages linked at the end of the guide or have a look at the grim-dawn forum on their homepage.
Basically there are some quests that are the same for both factions but the essential difference will be killing different people of the other group of believers or targets of the second faction they loath.

I have to say thank you, to the following person for reasons mentioned:

1. Strunz - thanks my friend for supplying me with all the screenshots for the Order of Death's Vigil

Additionally thank you all who read this guide of mine, even more so to those who like, favorite, comment and tell their friends about it.
It was quite a piece of work, making the Screenshots, cutting out the sections, renaming the pictures so that I would have an easier time inserting them in the guide and then all the formatting...
But I chose this for myself and I hope you appreciate it.

If you find any mistakes of whatever kind in my guide and/or are dissatisfied with something please tell me, too - I will have a look at it, whatever it may be.

A video from Tridord, showing every piece of Equipment from the factions [Build 27]:

The Grim Dawn Wiki pages for both Factions:
http://grimdawn.wikia.com/wiki/Order_of_Death's_Vigil
http://grimdawn.wikia.com/wiki/Kymon's_Chosen

The Grim Dawn Wiki pages for both Nemesis:
http://grimdawn.wikia.com/wiki/Zantarin%2C_the_Eternal
http://grimdawn.wikia.com/wiki/The_Iron_Maiden

The official Grim Dawn Forum Post from ReDeus contributed by the community on nemesis spawn locations:
http://www.grimdawn.com/forums/showthread.php?t=26148

A Reddit Post by /u/dolpiff contributed by the community on nemesis damage types:
https://www.reddit.com/r/Grimdawn/comments/40avql/what_damage_types_do_nemesis_mobs_do/

Currently this guide is up-to-date for:

• Build 27 - Guide created
  
• Changed "The Order of Death's Vigil" to "Order of Death's Vigil" and "The Kymons Chosen" to "Kymons Chosen" to match the in-game reputation screen; Rephrased some sentences [thanks to /u/kuvter]
  
• Added under "Allies Among the Ashes" the fact, that you will be able to rechoose on consecutive playthroughs
  
• Changed the table layout
  
• Build 28 - Added Component Blueprints and updated Blueprints and Items..
  
• Release v1.00 - Updated Order of Death's Vigil and Kymon's Chosen items (mostly items with skills got their skills buffed and enhancements were buffed overall). Added Elite lvl70 items for the Order and the Chosen.
  
• Crucbile v1.05 - Updated Order of Death's Vigil and Kymon's Chosen enhancements that were buffed in Hidden Path v1.04.