In the Beginning
In the beginning, humans were the weakest race. In a world of magic, humans who had no way of using mana to their advantage and were starting to get wiped to the brink of extinction, that was- until, an elf who fell in love with a hunter, a human split away from her race and taught humans the two paths to use magic.
Humans who didn't know how to use magic were classified as swordsmen who utilized their own life energy as a way to strengthen their swordsmanship by using the life energy as a way of coating their bodies and their swords in energy that eventually took the name of sword aura. By using sword aura, any part of their body could become a sword essentially as well as using even the flimsiest leaf as a weapons to cut off their opponents heads.
The other path humans learned as a way to use magic was to become magicians in which they would make a mana heart. The process of making a mana heart was fairly simple. Using the mana in the air and in their surroundings, they only had to coat their heart in mana allowing their bodies to be more receptive for mana no matter how old they would get. Once the mana heart was full, they go through an process to make a mana circle around that mana heart so they could increase the output and storing capacity of mana in their bodies. For each mana circle in their bodies, they could use more spells in conjunction to the amount of circles around their hearts. For instance, a Level one spell could be used by a mana heart with one circle, however a level two spell could not be used by a one circle mana heart. This by far was the hardest to do with people over 20 because for a person to become a magician.
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This was because mana is better to gather at a young age because when young, mana pores are open which allows a person to gather mana due to their sensitivity to magic, so as people became older those pores would close meaning they would have to do a certain acupuncture massage to force open their mana pores to allow collection of mana. And with this knowledge, the humans that were once on the brink of extinction pushed back and with more people learning how to fight back, other human nations were formed making humans a superpower.
With this, every race was pushed to their respective borders, Elves living in great forests, Beastkins living in villages as well as living in human kingdom, and so on. However, problems didn't end there with the appearance of the demon lord, a human tainted by dark magic, usually recognizable by the three crosses over the heart of the Demon lord. The Demon lord had a disdain with all life and commanded an army of demons to murder, pillage, and take over land for him. Races who were at the frontier of the assault were starting to get pushed back, and with that the races knew they had to do something. The next year after the Demon Lord started taking over and became a name to fear, a group of 5 heroes pushed back with amazing strength as the would call themselves heroes and help villages in need. The leader of the group showed a new path of magic becoming what is called a magic swordsman. And over the course of next 2 years, the demon invasion that once made ripples soon came to an end because the heroes sacrificed himself in a final battle with the demon lord winning but dying in the process and brought the world to a time of peace.