Demon

Demons are a race living on Gozta, the planet of this world. They were originally Aeokash, but when some of them wen through the Shadow Act, a curse to turn their souls into darkness, they became demons, with the sole purpose to kill humans.

Shadow Act
When the Aeokash and the forests were being killed by human expansion, Aeokash led by Aendensanire, or Gallow, went to the White Tree, the largest Tree, and the heart of all the forests. The Tree, in order to save itself and the forests, transformed Gallow and his followers, as well as the souls of the dead Aeokash and the trees who died from humans, into demons. Gallow becomes the representative of the White Tree, by absorbing the dark side of the Tree's soul.

Types of demons
There are several types of demons.

Mountain Demons: Demons that reside in the Aisling Mountains. They are known to be very aggressive and powerful. They even gain the power of fire, making them even more of a threat.

Forest Demons: These demons live in the forests and care of it. However, when they use their invisibility, the trees and all the life near them dies. They use their invisibility sparingly, only when attacking humans, to help the forest.

Water Demons: These demons survive underwater, usually in lakes, rivers, and even in the seas. They cannot resurface, because they adapted to live underwater. Because they are not able to leave water, they are not much of a threat, unless someone enters the water. One thing they can do is evaporate with water and travel through rain.

Powers
Demons have certain advantages, as well as disadvantages when fighting humans.

Advantages of:

Invisibility (able to use when matured, no human can see them)

Shape shifting (able to transform into different shapes and creatures, partially or as a whole)

Disappearing (able to disappear into the shadows when threatened)

Pack (able to fight with other demons, making them even stronger. They are pack animals)

Possess (demons, which are essentially darkness, can possess dead human bodies, covering their scent and making them seem like demondrirs)

Disadvantages of:

Invisibility (cannot use when young (vulnerable to humans), demondrirs can see them, and when using Invisibility, they kill life around them)

Shape shifting (no known disadvantage)

Disappearing (cannot flee through the shadows when there are no shadows)

Souls (can be absorbed by strong humans to create weapons capable of killing demons. Demondrirs are more powerful than demons.

Oath (demon cannot harm another demon who does not have intent to kill)