Blasphemies (or Terminus, as they were known in the days of Amaurot) are beings once composed of aether, but were consumed by dynamis and twisted into creatures devoid of reason. Their appearance on Etheirys signals the coming Final Days, the destruction of the star.
Long ago, during the time of the Ancients, the people of Etheirys were able to form the aether around them into anything they wished through their Creation magicks. Being made of incredibly dense aether, they were unable to interact with the mysterious force known as dynamis, however their creations were not as dense. When Hermes created Meteion in order to more closely study dynamis, he also created replicas of her to send to the various planets beyond their star to learn the meaning of life. However, upon discovering nothing but death and dying planets and people, Meteion became overwhelmed by the despair her sisters felt, and determined that the meaning of life is suffering and pain. She determined that Etheirys must die as well, in order to avoid such suffering and pain. Due to being a creation, Meteion's aether was thin enough for her to gain control over the 'dynamis, and she declared that she would bring about the Final Days.
Following the events at the Ktisis Hyperboreia, Meteion fled to the edge of the cosmos and began to "sing her song of oblivion", channeling dynamis into the planet. The sound of her song rang out to the planet, a strange sound that began affecting the creation magicks of the Ancients, twisting them into fierce, unthinking monsters. As panic spread through the star, the creation magicks began to run amok, birthing more and more of these monsters that slowly began to consume the world. This was only stopped by the Convocation of Fourteen by calling upon Zodiark and shrouding the world with aether. When Zodiark was sealed away by Hydaelyn and the world was sundered, the aether remained around The Source, protecting it and the much more fragile inhabitants who called it home.
In the modern era, the people of Etheirys are made of much thinner aether, and are therefore far more susceptible to the effects of dynamis. When the barrier tied to Zodiark is destroyed, dynamis is able to manifest and feed on the aether and negative emotions of the people, destroying the aether that they are made up of if they succumb to their despair. Due to being affected by emotions, the Blasphemies can be driven by a single-minded goal or wish the person once held. However, in most cases, the Blasphemies become violent beings devoid of reason. In the extremely rare occasion, a Blasphemy can become intelligent, capable of strategizing and commanding the other Blasphemies.