Dargonax was reputedly the third twilight dragon created by Sinestra. The first two were not named, but their instability saw them slain with relative ease compared to Dargonax. Hatched from a black dragon egg infused with the energies of the captured nether dragon, Zzeraku, Dargonax rapidly grew into a gargantuan beast nearly equaling the Dragon Aspects themselves in size. His ambition and cunning grew along with his body, and soon he harbored a desire to overthrow his "mother" and conquer the world for himself. Becoming arrogant of his own abilities Dargonax attempted to kill his "mother" at first chance only to freeze in place as Sinestra used the shards of the Demon Soul to control him. Later on when he learned about her creating more dragons like him, Dargonax becomes displeased as he feels that the his new brothers and sisters would be better.
During his development the blood elf Zendarin Windrunner secretly wished to take control of Dargonax as a magic source and his own personal dragon, and tried to do so with a final feeding to make him his slave. Sinestra had foreseen all however, and simply made Zendarin's betrayal a part of her plans, which resulted in his failure and escape from as an enraged Dargonax tried to kill him. Dargonax would later be called to battle the invaders of Grim Batol but the where able to free Zzeraku, who quickly engaged Dargonax in battle. As the two clashed Dargonax fully absorbed the dying Zzeraku, who had decided to try and save Iridi at the cost of his own life. During this time Zendarin stole Demon Soul (possibly as an alternate magic source having failed to take Dargonax, or as a secondary objective), the foul creation of Deathwing that had been destroyed by Rhonin years earlier. He would have pulled it off if not for Vereesa's intervention, which resulted in the destruction of the Demon Soul - and of Zendarin himself - when the stolen staff of the Naaru touched the artifact.
With his power strengthen and his new found freedom in the wake of the Demon Soul's destruction Dargonax, who had become frustrated at with Sinestra's attempts to control him, turned on his "mother" at this. As Dargonax attacked her the others noticed that Zzeraku's sacrifice had catalyzed the minor defective part within the twilight dragon that Iridi and her allies were able to exploit and finally defeat Dargonax, who as he burned away took his Sintharia with him
Like the earliest twilight dragons created by Sinestra, Dargonax had the power to vampirically drain magical energy from any source. He especially delighted in draining the power from dragons, and indeed this may be the very purpose the twilight dragonflight was created for.
Dargonax also seemed to acquire the powers or attributes of his victims, as when he completely absorbed the powers of the nether dragon Zzeraku, he gained the nether dragon's ability to shift into an ethereal form. This ultimately proved Dargonax's undoing however, as absorbing Zzeraku's energies caused a fatal destabilization of the twilight dragon's already unstable powers. Glowing as brightly as the sun, Dargonax burned away, seriously injuring his mother in death.
"I obey no one but myself... I am Dargonax, the Devourer of all, including you..."
"Good... good... and friends, they help friends, yes? Is that right?" (to Kalec)