Nihilia the Un-Queen of Dragons

After Voraagon the Dragon-King was hatched and crowned, the gods sought to give him a consort, and turn what was to be the evil of the dragons against Xyaxis. Thus, Shyndrall orchestrated the theft of the greatest dragon egg laid in the dark tunnels beneath Ilutzera, and brought it into the light. There, under sunlight and starlight it was incubated, until a deep, metallic-purple dragon was hatched. She was named Amaherens, meaning Dragon-Mother in the old tongue. For many years, she grew, and was nurtured, and cared for, and she found a deep and abiding love for her husband-to-be. Thus, she was named the Dragon-Queen, and Consort of Voraagon.
However, her nature poisoned her mind, and gave a crack for dark weeds to take root. Amaherens had been birthed in the darkness, and was created, initially, from the chromatic dragons of Xyaxis the Deceiver, and thus had fragments of his will in her. She fought for many years against her own greed and pride, but, after two centuries of rapid growth, she fell.
Xyaxis, preying on her pride, placed a hood over her eyes, so that she saw herself not as a partner and wife of Voraagon, but as his servant. A servant who should be master, who had been beaten down unfairly. She hid these feelings, and the whispers, from her husband, and the gods, and they were nurtured in her heart. The years she had spent mastering her own nature slowly unraveled, until she knew she was to lay the first clutch that would be fathered by the husband she had so recently been bonded with.
In their chambers, alone, Amaherens rejected her name and position, and attempted to slay Voraagon. With a mighty bellow, the Dragon-King fought his wife away, and she fled into the dark, nursing deep wounds, as the Deceiver whispered into her ear that all was as he had predicted; her husband had denied her the rightful place she deserved, and had turned her out when she tried to take it. Thus she found a dark hole, and slid deep into her earth, where she found warmth in the benighted halls of the deeps. There she laid her eggs, five of them, each a different color. She then fully allowed the greed, hate, and malice of her nature as a dragon of Xyaxis to enter her, and poured this into her eggs.
After she fled, Voraagon searched the skies and earth for her, only returning to his throne of rock after three months' of scouring. Even then, he sent his attendants out into the world, always seeking his beloved. When she did choose to reveal herself, though, it was in blood and fire.
Fifty years after her flight, the First Consort showed herself again, followed by her five first-born. Immediately they pledged themselves to Xyaxis the Deceiver, and set about carving swaths of death and destruction across Ulei'var.
Upon discovering her rampage, and with a heavy heart, Voraagon renounced his own queen. He named her Nihilia, the Un-Queen, and wept.
As she was unnamed, Nihilia's nature changed. No longer are her scales a shining purple, nor does she truly have scales at all. Her flesh was turned to an oil-colored, ever-shifting ooze over her bones. She shifts these constantly to suit her needs, appearing as whatever sort of dragon suits her fancy, though she loathes taking the form of the metallic dragons of the gods. She much prefers to take the form of a wrathful red, or even appear as a writhing, oil-slicked dragon of unnatural shape, devouring all before her.
Nihilia's rampage was bloody, and her service to Xyaxis was fruitful. She slithered into the fortress at Ilutzera, and from there continued to hatch the earliest of true dragons. There she was protected from attempts on her life, and many would-be assassins were tortured and fed to Nihilia in her dark lair.
After the destruction of Ilutzera, Nihilia fled into the mountains, ready to help her master come fully and bodily into Ulei'var, so that he could oust the other gods and take world for his own enjoyment. Using her ability to bore a small hole between worlds, she would often ferry orders from Xyaxis, or creatures from the dark plane of Azpiya. On the eve of her king's victory, she writhed through the space between worlds, ready to make way for his arrival in Ulei'var. However, all was not well with their plan, for the Clockmaker, the Lord of Balance, plunged his own blade through his chest, erecting the divine barrier around Ulei'var, locking all of the gods out of the material world. This left Nihilia trapped in the void between Azpiya and Ulei'var, scratching at the barrier, howling in mindless rage. She plots still to return, and occasionally pushes polyps of her will through the barrier.
Nihilia is wrathful, but patient. Soon enough, her cultists will gather, and tear a hole into this barrier wide enough for her true self to come through, and Ulei'var will know the Un-Queen's fury. And then, once she has burned and purged to her dark heart's content, then shall she, maybe, tear down the barrier from within, to allow her lord and king to enter the world and make it his throne of ash.