Thus the Necrons were born and the C'tan and Necrons had their terrible revenge on the Old Ones.

Unfortunately, the C'tan used the same living metal to seal the Necrontyr's minds inside skeletal constructs, turning the race into undying slaves that would help the C'tan harvest all life from the galaxy. A bargain was struck: the Necrontyr would provide these beings, the C'tan, with bodies made of the living metal the Necrontyr used for their spacecraft in return, the C'tan would grant the Necrontyr immortality. They soon realized they had no hope of success, until they discovered powerful energy beings lurking within their star. In a fit of jealousy, the Necrontyr declared war. The Necrontyr eventually encountered the Old Ones, an enlightened and long-lived species, and pleaded with them to share the technology to increase their lifespans - but, again, to no avail.

Their bodies wracked with sickness, their lifespans shortened by radiation and plasma storms, they developed advanced technology to try and compensate, but to no avail. In the galaxy's distant past, before humanity, before the Eldar, there was a race known as the Necrontyr that clung to life on a bleak world under a hostile sun. In Warhammer 40,000, the Necrons are an ancient race of robotic aliens, once a galactic superpower and now slowly becoming a threat again.

Warhammer 40k necron dynasties