The Fiends

Fiends. The plague of the millennium. Ever since they surfaced from deep within the earth long ago, they have been a constant threat to all life.
Fiends are often driven to prey on the living, which makes them a constant plague on the planet. Born from the wondering souls, it is still uncertain why, but when the souls of the dead clump together over Aether, they assume a warped physical form known as a Fiend. These souls wander across the lands in search of even the finest pieces of Aether, collecting it from the air, water, and soil as they travel. Once they absorb a large enough deposit of Aether, they are reformed into Fiends. Each Fiend is a reflection of the soul or souls as they were in life, ranging from an embodiment of their greatest desire to an appearance reflecting a misdeed. Most unsent souls will eventually become fiends, especially of those who held strong desires, regrets, or did not fill their lives with a satisfying enough ambition.
It is believed that they envy the living. And in time, that envy turns to anger, even hate. And while these souls remain unsent, they become Fiends as they give into their hate. When a Fiend is not hunting the living, they usually wonder the lands in search for more Aether. Their attraction is not suspended from when they were souls but rather intensified. Either as a soul or a Fiend, this attraction will eventually lead them deep underground, navigating through caverns and caves, eventually making their way into dungeons. And the more Aether is collected in one location, the wider the reach is. Some souls or Fiends have been known to travel hundreds of miles when large enough collections of Aether are felt. And because the Dungeons still contain some of the largest concentrations of Aether, they are constantly being populated with more and more Fiends. Equally, the cities that grow their societies with large amounts of Aether, are constantly under threat from an inflow of Fiends.
As Fiends are exposed to constant concentration Aether they continue to reform, becoming more powerful and dangerous Fiends. The longer a Fiend has to absorb Aether, the more difficult it becomes to destroy it, and if left unchecked could eventually grow to colossal scales and terrible might. This is why efforts are made to reach deeper parts of the Dungeons, to help control and reduce the number of these powerful Fiends. Though it is significantly more challenging to make one's way down to the lower reaches of a Dungeon from the number of Fiends that are encountered along the way, as well as their strength intensifies.
In addition to their strengths, Fiends do not remain dead when killed. The souls that are held within them and freed upon its death, are prone to transforming into a Fiend once again. If it wasn't for the Sending Process, a technique used to cleanse the souls of their malace to prevent them from transforming, the threat of Fiends would be infinite.

TYPES OF FIENDS There are 3 types of Fiends categorized by Beast Fiends , Elemental Fiends nd Nightmare Fiends
CLASSIFICATIONS OF FIENDS There are 6 threat rankings of Fiends set from easiest to hardest. These are F, D, C, B, A, and S threats.