Mana is a very versatile and powerful energy, although often considered rather mysterious in nature by most intelligent beings, it can be used to craft spells and power varying constructs. It is often used by simply being controlled by outside sources such as living beings and tools to change its nature into what is required. This is known as regular magic and Mana control.
Arisia was a world overflowing with such energy, giving birth to multiple species and granting them intelligence along with the ability to manipulate the Mana permeating the air.
Humans, Elves and Dwarves were an example of such creatures, living in a time that gave birth to a great amount of heroes and legends thanks to the endless Mana granted to them. However such a blessing was not eternal as the world's Mana quickly got depleted and left the future generations powerless for a time.
In an attempt to counteract the situation, the races decided to create their own synthetic Mana and change the course of their future brought by the weakening of the world. The Elves decided to create artificial Mana heavily influenced by nature and the sun, giving it a very powerful life energy. The Dwarves on the other hand chose to create theirs by copying the power from the world's core itself, harnessing the power of lava, minerals and mountains, therefore creating a very overwhelming power. The Humans however, were unable to create anything and were forced to beg other races in hopes of being taught their ways.
Sadly, they were all rejected and left without choice. While unable to grasp power from the synthetic Mana the other races created, they decided that they would grasp the power from themselves and resorted to using human sacrifices as a source of strength. This was not an acceptable path to power though, and it quickly went wrong, creating a new race in the process.
This species was later known as Demons, with the Demon King as their leader. Obviously this new race was not a friendly one and they destroyed multiple human kingdoms after their birth, nearly driving them to extinction and threatening all the other races due to their overwhelming power. The world was not without mercy however, as it quickly created a new type of creature to counteract this threat that it viewed as a virus, the Dragon Kin. The races were quickly allied with the Dragon Kin as their leaders and they swiftly eliminated the threat that the Demons posed, although it wasn't without a lot of losses.
After the great war with the Demons, the Dragon Kin were sure that such an event was bound to happen again and they warned the other races about it. They then led every species towards creating a long lasting alliance with all the intelligent races.