Demon

One of the most mysterious species, demons is one species you shouldn't trifle with. The interesting thing about them is that the 10th didn't create them. Because of this, the 10th look down upon them. They consider them to be unpredictable and too dangerous to let live on the mortal plane. However, not all demons are evil. They're simply a reflection of humanity. It's just that the reflection tends to be more negative than positive.
Demons can be born and made in several different ways. For the easiest, demons can be born from the raw emotion. Usually, it requires massive amounts of emotional energy for a demon to be born. Depending on what emotion is being felt determines almost everything about a demon. Another way is reincarnation. Whenever a mortal dies, there's a possibility of them becoming a demon. This is only possible if the mortal has a strong will. If they do, they'll wake up as a demon. It's possible for the former mortal to retain their memories, but it's rare for them to have their humanity intact. A mortal that's still alive can become a demon. Although, this is only possible is if a demon with significant strength changes them.
There are four different types of demons. There's lesser demons, regular demons, arch-demons, and free-demons. Lesser demons weaker versions of regular demons. Regular demons have full access to their demonic powers. Arch-demons have a special trait and are able to control lesser and regular demons. Free demons are demons who aren't bound to the Underworld. That being said, they vary in power. This term can be used to describe an Arch-demon who has escaped the Underworld. One trait they all share is the ability to posse mortals.
Most demons live in the Underworld. They're in a constant struggle to survive. That's because demons are constantly trying to kill one another. Whenever a demon kills another demon, that demon absorbs the soul and becomes stronger. Demons want power and to be feared, while others want solitude. It's kill or be killed in Underworld, and mercy is a rarity.

Basic Information

Anatomy

They're more or less mutated versions of different species.

Biological Traits

Demons are made of out of spiritual energy. Depending on how the demon was born, determines how the traits of it.

Genetics and Reproduction

Demons can't reproduce with their own kind. For them to have an offspring, they would need to find a willing or unwilling mortal.

Growth Rate & Stages

There's lesser demon, then the regular demon, then arch-demon. The more souls a demon eats, the faster it grows.

Ecology and Habitats

They are mostly located in the Underworld. There has only been a few know cases where a demon has been able to escape.

Dietary Needs and Habits

Demons don't need to eat or produce waste. Although they do need to rest. Demons do however eat souls. Souls are like mini power boost to demons. Eating tons of souls will increase the power of a demon.

Biological Cycle

As time goes on, a demon can only get more powerful.

Additional Information

Social Structure

The more power you have in the Underworld, the more feared and respected you are.

Geographic Origin and Distribution

Almost all demons are trapped in the Underworld. There's only a few that are currently on the mortal plane.

Average Intelligence

Most of them are of average intelligence. Weaker demons tend not to think for themselves.

Perception and Sensory Capabilities

Demons have enhanced senses. The thing that sets them apart is that they're able to sense different forms of energy and power.

Symbiotic and Parasitic organisms

All demons can possess mortals, but it's more effective to make a contract with a mortal. Contracts allow mortals to draw on the power of a demon. What a demon gets out of it is tied to the contract. Most of the time it's living in the mortals body or having ownership over the soul.

Civilization and Culture

Naming Traditions

Names are based off how the demon was created, or their powers or traits. If the demon was human once, their name could be related to their death.

Major Organizations

Underworld Kingdom

Beauty Ideals

Beauty doesn't mean anything to a demon. This is because they're able to change form at will.

Gender Ideals

Male demons are expected to be powerful while females are expected to use their charm and bodies to get what they want.

Courtship Ideals

Most demons tend to want a willing partner. If a demon forced them self onto a mortal, the mortal is more likely to have a miscarriage. Some might go as far in as to trick a mortal into having their spawn.

Relationship Ideals

Demons want to find partner to bare their offspring. They prefer those with a strong will.

Common Dress Code

There really isn't a real dress code, but if you're a regular demon and up, you're not going to be naked.

Common Customs, Traditions and Rituals

Demons that are weak usually ally themselves with the strong.

Common Taboos

Escaping the Underworld is strictly forbidden. If you fail, you will be sentenced to death.

History

Ever since the first human was created, demons have always existed.

Interspecies Relations and Assumptions

Some demons view the other species as food or a host. While others think of them as a means to have children. Although some truly do love their mates.

Genetic Descendants

• Vampire

Lifespan

They can't die by aging. However, they aren't immortal either.

Body Tint, Colouring and Marking

Usually when they're trying to hide their form, a demonic marking is somewhere on their body. This marking sometimes appear when the demon is feeling a strong emotion.