Elf

The Elves are the only mortal race that were alive during the Age of Spirits. Initially, the Chara Spirits created them as an attempt to create a race that could nurture and protect the loss of Essence in the realm that would eventually be known as the Mortal Realm. While the elves did a fair job at nurturing Essence and ensuring it grew; they were also creatures who could tap into pure Essence. Over time the elves began to experiment and evolve; no longer caring and nurturing Essence as they once did.
Towards the end of the Age of Spirits; the elven societies of the second realm caused the Chara Spirits to grow angry. Essence in the world was evaporating and the Spirits were forced to flee back to The Eternal Domain in order to survive. What the elves did is only known to the Chara Spirits who managed to survive. It was decided by the Spirits that the elves should be punished and so the Spirits invoked powerful magic.
All of the Elves were forced to forget their society and magic from the Spirit Age; they retained their knowledge of how to survive and their families but none of their history.