Demons

Demons are a collective name for the sentient life (mostly under the influence of Lucifer) that live in the Underworld.
Known as demons, they are a vast term for lifeforms of both silicon basis and tungsten basis. Demons have been evolving on the planet for about 2.5 billion years, yet surprisingly they had not made much technological or societal progress. Demons are lifeforms that the vast majority of are born with very low levels of natural determination. They didn't have much resolve or will-power, meaning they wouldn't ever do much. In that 2.5 billion year time span, the most ancient demonic society progressed was small villages and clans scattered about the underworld. The biggest of which housing over 60,000 individuals. 
This all changed about 300,000 years prior to the salvation event, when Lucifer discovered the potential within demons. He began making unfathomably cruel experiments on their people for the next 100,000 years, until he was finally able to unify a demonic body with a human soul, giving demons the ability to harness resolve. Since demons were not infused with spirit they generally remained emotionless and cold, making them the perfect soldiers for Lucifer's plans. 
== Recent History ==
After Lucifer's meddling with demonic evolution, demon society skyrocketed. Within just a few thousand years they had completely unified as a people, creating cities and technology comparable to earth and even better in most cases. After a while they were somewhere between a type 1 and type 2 civilization on the kardashev scale. Of course this was all possible due to Lucifer, whom they hailed as their God, pleasing Lucifer greatly. 
As they were only pawns to him, Lucifer began to mold the mostly peaceful demon society into an extreme militaristic one for his benefit. Every demon would be put through intense and unrelenting training to make it into the militaries ranks. Those who could not make the cut were forced to work menial tasks and were ostracized by society. They began to only view others based on military rank, making them work even harder to be promoted. 
== Physiology ==
The physiology of demons are very vague, as the wide range on them makes it impossible to classify at such a scale. Though there are a few aspects that they all share. Tungsten based demons are generally more animalistic in behavior. They aren't capable of complex thought and their tough skin usually relinquishes them to the task of brutes. The silicon based demons are capable of higher thinking, strategizing, and other forms of sentience. They are also much more widespread making up more than 80% of the demonic population. They are all taught to speak and read all forms of demonic languages, ancient and new, and most know a wide array of hell based magic. 
Along with this, an important feature of most demons is that they cannot breathe oxygen, as it is highly toxic for them. To combat this demons on earth must wear special masks on their face that syphon in air from their home planet, with a few exceptions. 
=== Humans Turned Demon ===
Powerful enough demons have the ability to make deals with humans or other lifeforms to make them demons in exchange for something. Demons that originate as humans are generally much stronger than normal demons. Their increased soul and spirit along with having their original mind and body makes them much more complete and unified. Examples of demons that were originally human are Angela Jones and Hellbender, while an example of a demon that originated from the underworld is Itazura Akuma. 
== Abilities ==
All demons within Lucifer's ranks are taught basic forms of combat as well as extensive combat training in styles that work best for their physiology. Demons are also taught to use a variety of hell magic, which is a magic type that specializes in attack power and punishment, gaining its uniqueness from the harsh environment of the planet. Many of the spells use fire, mental attacks, etc. 
=== Soul Steel ===
Soul steel is a type of metal that is forged in the underworld from the tungsten that is found near stonewalla breeding sites. The tungsten is then melted to create a steel alloy, which a soul is melted into as well, to create an extremely durable and versatile metal. Another useful quality of soul steel is its ability to grow stronger if it takes souls. This leads to its use in weapons and armors most often. 
==== Purified Soul Steel ====
When tampered with by holy magic, soul steel can become purified soul steel. This purified form weakens demons significantly, so it is seldom used by them, though the properties of the metal can't be denied. Purified soul steel can no longer reap souls to get stronger, yet increases the strength of previously reaped souls tenfold by the point it gets purified. Along with this it takes a much lighter color, and gains an extra protection to magic attacks. 
== Gallery ==
File:Hellbender in hell.png
File:Itazura akuma.png
File:Demondust.png
== Trivia ==
* Surprisingly, demons were not considered for the series until much after Gods were already planned