There was once the being of darkness who roamed the realm of heaven without any purpose, it was hailed as the strongest transcendent being to exist in the realm.

 But it had one problem, because of its power many tried to use it for their own personal gain and profit.

 Scarred by the things done to it by others and being shunned from heaven, it shut its heart in the cold darkness of space, but as it was about to give up hope a small warm light entered its space and when it confronted the light, it came face to face with another being like it who was shunned from heaven was roaming the space without hope but a purpose to help others like it.

 The being of light who had finally found its hope in the deep dark cold space finally rejoiced and after spending considerable time with the being of darkness it asked the being to stay with it forever, the being of darkness was overjoyed at finally finding a partner to commit to gracefully accepted its offer.

 But this was seen as a negative influence by the realm of heaven as two powerful beings coming together, this made the residents of heaven drown and jealousy and envy as there was no powerful being that was on their side and regretting their decision of shunning the couple.

 Hence, heaven with their allies declared war upon the newly formed couple. There was immense one-sided bloodshed and countless residents of heaven and its allies perished, but the heaven in a last-ditch effort to win the war tried targeting the being of light.

 Strongest Residents of heaven combined their power and formed the ultimate weapon that they hoped to use it on the being of light. 

The being of darkness somehow caught whiff of this plan and rushed to its partner, but it was too late the plan was already put in motion and as he arrived near its partner, the being of light being distracted by the strong residents of heaven, the weapon was thrown towards the being of light.

 Being of darkness rushed towards the being of light and tried destroying the weapon but failed as the weapon got closer and closer towards its partner, the being of darkness had no choice but to but to stand in front of the being of light and sacrifice itself for its partner. The weapon pierced the once strong being of darkness and reaped its consciousness, being of light who did not know what had happened turned towards its partner to only to find a lifeless body.

 Emotions of fury, anger, hatred and despair resounded through the realm and an ear-piercing scream resounded throughout the world. The residents of heaven  realized the mistake they had made. 

The light once emitted by the being of light became duller, darker and more red. The distraught being of light who only wanted peaceful life with its partner, held the lifeless body of its partner and absorbed both its body and weapon

With one last bright light filled with multiple colors exploded with a great bang absorbing the once almost eternal heaven and all its realms and thus, combining all of the power and matter the world of Atheus was formed where power was bestowed to each of its residents in some or the other form.

~~~Source: The Church of PONIFEX

Since the ancients who could manifest and control this power through the process of ACFF Cycle hence, dubbed themselves as "Atheians".

Thus, following after the power was dubbed "Atheka".