In the universe of Kingdom Under Fire, there is something called the "Flow of Dimensions". Two gods, that have existed since the very birth of the universe, take turns ruling the land. Each "age of light" is followed by an "age of darkness".
However, sometimes when those two ages simultaneously exist as each age flows in a different dimension, it creates an unbalance in time, and this connects two dimensions together as a result. The event that people call "The Great Diastrophism" was also triggered by this. The crack that was opened by this event was the cause of bringing Encablossians into the Bersian continent.
They were originally the creatures living in the age of light, but were swept to the age of light while the age was changing, and changed their form in order to adapt to their new home mutating their body, the process that was very painful. However, they survived from it in the end.
But the Encablossa, master of the dark dimension, treated them as if they were expendable during the holy war with the age of light. Such was their destiny.
The leader of Encablossians, Aleph made a powerful spiritual solidarity that bound the race into one, and this broke them free from the cuff that Encablossa put on them and made it possible for them to escape from the dark dimension through a crack caused by the unbalance in time.
After they made their way to the age of light, they called themselves liberators and fought against their former master Encablossa only to find out that he and his armies were too strong for them.
So they seek a way to become stronger, and one of the solutions they came up with was to take advantage of Encablossa's power.
They figured that only if they could apply the right amount of Encablossa's power to their body which was mutated into something well-suited to live in the dark dimension, they would be able to get stronger physically and furthermore, to use some of Encablossa's divine power.
Their attempt was successful in the end, and the Encablossians that managed to achieve more powerful body and the ability to use the dark blaze signaled the beginning of the Berserker class.
Because it is difficult for them to control the power of Encablossa they possess to the extent it will only damage the enemies, they always charge at the very front line in battle. This suits them perfectly for they don't have to restrict their power worrying about hurting their friendlies.