The terrible wars between the Old Ones and the Necrontyr that followed, known later in Aeldari myth as the "War in Heaven," would fill a library in their own right, but the Necrontyr could never win. Their superior technology was consistently outmanoeuvred by the Old Ones thanks to their mastery of the Webway portals and Warp Gates. The Necrontyr were pushed back until they were little more than an irritation to the Old Ones' dominance of the galaxy, a quiescent threat clinging to their irradiated world among the Halo Stars, exiled and forgotten. The Necrontyr's fury was cooled by their long millennia of imprisonment on their homeworld, slowly transforming into an utter hatred towards all other forms of intelligent life and an implacable determination to avenge themselves upon their seemingly invincible enemies.
But in the face of defeat, the always fragile unity of the Necrontyr began to fracture once more. No longer did the prospect of a common enemy have any hold over the disparate dynasties. Scores of generations had now lived and died in the service of an unwinnable war, and many Necrontyr dynasties would have gladly sued for peace with the Old Ones if the ruling Triarch had permitted it.
Thus began the second iteration of the Wars of Secession, more widespread and ruinous than any that had come before. So fractured had the Necrontyr dynasties become by then that, had the Old Ones been so inclined, they could have wiped out their foes with ease. Faced with the total collapse of their rule, the Triarch searched desperately for a means of restoring order. In this, their prayers were answered, though the price for their species would be incalculably high.
It was during the reign of the Szarekhan Dynasty's Silent Kings that the godlike energy beings known as the C'tan first blighted the Necrontyr. It is impossible to say for certain how the Necrontyr first made contact with the C'tan, though many misleading, contradictory and one-sided accounts of these events exist. The dusty archives of the Tomb World of Solemnace claim it was but an accident, a chance discovery made by a stellar probe during the investigation of a dying star. The Book of Mournful Night, held under close guard in the Aeldari Black Library's innermost sanctum, tells rather that the raw hatred that the Necrontyr held as a species for the Old Ones sang out across space, acting as a beacon that the C'tan could not ignore.
Another account claims that from the earliest days of their civilisation, Necrontyr scientists had been deeply engaged in stellar studies to try to understand and protect themselves from their own sun's baleful energies. After long, bitter centuries of searching for some power to unleash upon the Old Ones, the Necrontyr researchers used stellar probes to discover unusual electrodynamic anomalies in the oldest, dying stars of the galaxy. In the complex skeins of the energetic plasma of these suns, the Necrontyr found an intelligence that was more ancient than that of any of the corporeal species in Creation, including the Old Ones, entities of pure energy that had spawned during the birth of the stars eons before.
These entities had little conception of what the rest of the universe entailed when the Necrontyr first found them, feeding upon the solar flares and magnetic storms of these bloated red giants. Here was the weapon the Necrontyr had long sought to bring about the downfall of the Old Ones, beings they believed were the progeny of the death-god they had long worshipped. Howsoever first contact occurred, the shadow of the C'tan fell over the oldest Necrontyr dynasties first.
The power of these star-born creatures was incredible, the raw energy of the stars made animate, and the Necrontyr called them the C'tan or "Star Gods" in their own tongue. The C'tan were dispersed across areas larger than whole planets, their consciousnesses too vast for humanoids to comprehend. How the Necrontyr ever managed to communicate with them is unknown to the Adeptus Mechanicus. Understanding that such diffuse minds could never perceive the material universe without manifesting themselves in a material form, some Necrontyr actively sought the C'tan's favour and oversaw the forging of physical shells for the C'tan to occupy, cast from the living metal called necrodermis that they had once used for their colony torch-ships.
Fragmentary Aeldari legends tell of translucent streamers of electromagnetic force shifting across space as the star vampires coiled into their new bodies in the physical realm across an incorporeal bridge of starlight. Thus clad, the C'tan took the physical shapes of the Necrontyr's half-forgotten gods, hiding their own true desires beneath cloaks of obsequious subservience.
Incomprehensible forces were compressed into the living metal of the necrodermis bodies which the Necrontyr had forged as the full power of the C'tan at last found form. As the C'tan focused their consciousnesses and became ever more aware of their new mode of existence, they came to appreciate the pleasures available to beings of matter and the other realities of corporeal life. The deliciously focused trickles of electromagnetic energy given off by the physical bodies of the Necrontyr all about them awakened a new hunger in the C'tan very unlike the one they had once sated using the nourishing but essentially tasteless energies of the stars.
So it was that one of the C'tan came before the Silent King Szarekh, the last of his line, acting as forerunner to the coming of his brothers. Amongst his own kind, this C'tan was known as Mephet'ran, the "Deceiver," for he was willfully treacherous. Yet the Silent King did not know this C'tan's true nature, and instead granted the creature an audience. The Deceiver spoke of a war, fought long before the birth of the Necrontyr, between the C'tan and the Old Ones. It was a war, he said, that the C'tan had lost. In the aftermath, and fearing the vengeance of the Old Ones, he and his brothers had hidden themselves away, hoping one day to find allies with whom they could finally bring the Old Ones to account.
In return for this aid, the Deceiver assured, he and his brothers would deliver everything that the Necrontyr craved. Unity could be theirs once again, and the immortality that they had sought for so long would finally be within their grasp. No price would there be for these great gifts, the Deceiver insisted, for they were but boons to be bestowed upon valued allies.
Thus did the Deceiver speak, and who can say how much of his tale was truth? It is doubtful whether even the Deceiver knew, for trickery had become so much a part of his existence that even the C'tan could no longer divine its root. Yet his words held sway over the Silent King who, like his ancestors before him, despaired of the divisions that were once again tearing his people apart. For long solar months he debated the matter with the other two phaerons of the Triarch and the nobles of his Royal Court.
Through it all, the only dissenting voice was that of Orikan, the court astrologer of the Triarch, who foretold that the alliance between the Necrontyr and the C'tan would bring about a renaissance of glory, but destroy forever the soul of the Necrontyr people. Yet desire and ambition swiftly overrode caution, and Orikan's prophecy was dismissed. A Necrontyr year after the Deceiver had presented his proposition, the Triarch agreed to the alliance, and so forever doomed their species.
For their part, the Necrontyr soon fell into awe of their discoveries and the C'tan moved to take control over their benefactors. The powers of the C'tan manifested in the physical world were indeed almost god-like and it was not long before the C'tan were being worshiped as the Star Gods the Necrontyr had named them.
Perhaps they had been tainted by the material universe they had become a part of, or perhaps this had always been their nature even when they were bound to the suns they fed upon, but the C'tan proved to be as cruel and capricious as the stars from which they had been born. They soon revelled in the religious worship of the Necrontyr and feasted upon the electromagnetic life energies of countless mortal slaves.