This guide is here to help players efficiently farm a lot of arcane crystals, quickly in the early ladder, before they have access to high level characters.
There are two main methods of crystal farming that i will focus on here: Mephisto and Nihlathak.
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Here are the pros and cons of each method:
Mephisto:
+ Can be done as early as Act 3
+ Almost every character can run this relatively easily
- Layout is varied (What this guide mainly is for, turns this to a pro)
- Minimum of 2 Shards per run, a bit longer than the Nihlathak route.
Nihlathak:
+ Layout is small and very easy once you know it
+ Minimum of 3 Shards per run, a bit shorter than the Mephisto route.
- Must be in Act 5 to run it
- The area can be very deadly for a lot of characters early on!!!
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Mephisto Farming

Requirements:
* Character that can survive in Durance and kill mephisto.
* Map reveal from Meshif in act 3.
* High movement speed is preferred, but not required.
The problem with farming mephisto is that there are two "exits" in the layout, this requires you to possibly search both exits before you find the correct one that leads to The Seat of Hatred.
However, if you know how the layout works, you will be able to find The Seat of Hatred with 100% success on the first try, every time.
Here is how it works:
The waypoint in Durance Level 2 will spawn in one of four different tile positions: Top Left, Top Right, Bottom Right and Bottom Left.
Once you know which tile your waypoint has spawned in, you can easily figure out which one the correct exit will be in.
In Durance, the correct exit tile will spawn as shown in this picture:

If that's a bit confusing, don't worry. I have made a few examples to properly showcase how this works in-game:
Example One

In this picture we have the waypoint located in a "Bottom Right" tile, which means that the exit tile will be in a "Bottom Left" tile.
Example Two

In this picture we have the waypoint located in a "Top Left" tile, which means that the exit tile will be in a "Top Right" tile.
Example Three

In this picture we also have the waypoint located in a "Top Left" tile, which means that the exit tile will be in a "Top Right" tile.
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Nihlathak Farming

Requirements:
* Character that can survive in Halls of Pain and kill Nihlathak.
* High movement speed is preferred, but not required.
* No map reveal required.
The layout for farming Nihlathak is very simple, and once you learn the three possible routes, you will almost be able to run to him with closed eyes.
To find Halls of Vaught, in which Nihlathak hides, just determine the waypoint that you have from the picture below, and then follow the route:

Once you get to Halls of Vaught, things get a bit trickier.
If you use Map Reveal, simply move the map to see in which of the four locations that he has spawned.
If you don't use map reveal, then you must find the following wall painting on one of the four marked locations on the map. Once you find it, go down that path and kill Nihlathak.

That's it for this guide. Please leave any feedback and/or any mistakes you find in the comments!
-ShadowDawn