The Hidden was a strange creature even before it was talked down out of the aether. It had watched It’s (siblings) while they had sported among the stars, and It had kept Itself unknown to them. It longed to join them, but was fearful of them, for It was the last spawned and least powerful among them. When the Necrontyr, full of hatred for the Universe and their Creators offered the C’tan bodies, It hung back, not wishing to be noticed.
Eventually, It’s curiosity won out over It’s fear, and It was made incarnate. It was shocked by the sensations of It’s new form. Things It had before noted as mathematical abstractions it now felt, and felt them all the more powerfully for never having felt before. It, who had bathed in the fires of Creation, could now feel the breeze. Admittedly, It was hungrier than It had been, but that was what the sentients were for.
It lacked It’s (siblings?) strengths. It wasn’t as crafty as the Deceiver, nor as widely versed in technology as the Dragon. It decided to adapt, by taking the best tricks from both. From afar It watched them, and finally It believed It had found something It could do that none of It’s (siblings?) could, a way to finally best them.
When the Great Devouring began, the cannibalistic battles that pitted C’tan against C’tan, It fled in It’s ship of living metal, taking with It a great number of dissembled scarabs and tomb spyders. It was caught by one of it’s (siblings?) and devoured, that (sibling?) being devoured in turn by another.
However, the Hidden had played It’s final card. Desperately studying the hardware and software of the mechanical insects as It fled through space, It had made a breakthrough. It had hidden a copy of Itself inside the code of the machines, a copy with It’s core personality and a hatred of the other C’tan. When It’s physical form was destroyed, a copy of It lived on inside the scarabs and tomb spyders.
Unfortunately, in the attack by It’s (sibling?) most of the swarm was destroyed. With it went much of the Hidden’s personality. All that was left was the overwhelming hatred of the C’tan, and an innate caution. This caution caused what was left of the swarm to go to ground on a planet, and begin creating many more members
During the years when it’s (siblings?) slept, the swarm grew in size. The Hidden slowly regained It's memories, and began formulating a revenge. It sent parts of Itself off on journeys to tomb worlds known to It, seeking news of It’s (siblings?). There, It slowly converted the sleeping Necrons to It’s allegiance. When It had need of souls, it would descend on a carefully chosen, isolated planet and devour it down to the bedrock. These actions were generally blamed on the Tyranids.
Now, It’s (siblings?) have awakened and at last It knows where they are. Lacking the technology of the Necrontyr, It has been unable to re-incarnate Itself. It has managed to store Itself inside a Monolith however. The swarm has grown over the years, until it can block suns with it’s passage. With turncoats in It’s (siblings?) armies, and the advantage of surprise, the Hidden believes it can achieve It’s revenge at last.
