The Devourer is the chief antagonist of the D-Verse and its only source of entropy.
When it was first created, the Pantheon had nine members, the youngest being Parvait, Goddess of Destruction.
Parvait was graced with a light olive complexion, liquid-smooth and free of blemishes (much to Bethany's chagrin), and a crown of jet-black hair somewhere between wavy and curly that fell to the middle of her back, always looking vaguely disheveled but not unattractive. Her eyes, when open wide to take in her surroundings, held a curious hunger in their coal-black depths; this suited the goddess's thin, waifish figure, which she most often wrapped in a simple white sheet, just barely thick enough to obscure her and often tenuously held up by one arm.
Often the Goddess of Destruction would be found asleep on her personal couch, little more than one long, white cushion with one end raised as a headrest and four wooden legs to keep it off the floor. The more she destroyed, the more she slept; and Parvait was always at her best immediately after waking, though she never discussed the content of any of her dreams.
As time passed, Parvait became continually more absorbed by her chosen role, destroying things out of a sense of obligation rather than mere necessity. She turned a deaf ear to the other Deities when they asked and then later demanded that she stop, continuing her reign of destruction over all creation - yet not out of malice, but rather duty, in her own eyes.
And then, one day, the goddess simply laid down upon her couch and fell into a deep slumber from which no one could wake her, for no discernible reason.
The Pantheon took this respite from the constant wanton destruction of creation as an opportunity, and used it to discuss what should be done about the situation. The Deities put forth a number of ideas, but the problem still remained that it was difficult to force Parvait to do anything, including stop. Only while she was asleep did destruction cease.
Eris stepped back from the heated argument momentarily, and was shocked to see the entirety of creation in the process of violently tearing itself apart. Casting her gaze over to the couch where Parvait slumbered, she was shocked yet again as she beheld a satisfied smile on the goddess's normally expressionless face. With a heavy heart, as the sleeping girl was more dear to her than any other Deity, she brought the issue to the rest of the Pantheon.
Not wasting a moment, all eight Deities stood as one and surrounded the couch, beseeching the Source to allow them to stop Parvait's rampage by any means necessary. But the Goddess of Destruction opened her eyes, still smiling faintly, and merely whispered "Goodbye."
And then her body, and essence, dispersed into the very fabric of creation.
Parvait's dispersal spread the effects of entropy throughout the entire D-Verse, which had never before been under the influence of such a destructive force. Thus, the whole of creation began its gradual slide toward complete and utter ruin.
Furious at this catastrophic turn of events, Dio swore to eradicate Parvait's influence completely, naming her the Devourer and enlisting the rest of the Pantheon to fight at his side. Even Eris accepted this path in the end, striking the former goddess's name from her mind - if perhaps not entirely from her heart - and focusing her abilities on the monumental task of purging and rebuilding all creation.
The Devourer proved to be near-impossible to eliminate, and the best the Pantheon managed was partial containment. Only a few places in the entire D-Verse were kept free of the corruption and decay brought on by the Devourer's grasp.
Worse still, the existence of the Devourer itself - now considered a non-person, merely an entity - brought forth a framework to empower Void magic, which exists only to punch holes in the D-verse itself, ripping apart the physical plane and the aether alike.
"Of All Creation", which was penned some time later, intentionally avoids any mention of the Devourer's predecessor, or indeed anything at all involving the Goddess of Destruction.