When completed, these constructs were intended to close off the Warp from the material universe entirely, utterly destroying any living creatures with a soul, leaving all other life in the galaxy as nourishment for the C'tan.
The C'tan hate the Warp and its psychic energies (even as they crave the living energies of organic beings) and had the Necrons construct a series of blackstone pylons on the world of Cadia and other planets across several sectors in the Segmentum Obscurus. The C'tan Shard of Mephet'ran the Deceiver. The C'tan used the hatred of the Necrontyr towards the ancient species called the Old Ones to help them gather the more appetizing energy emitted by living beings that they came to crave. They are able to interact with the physical world thanks to the technology of the Necrontyr which transferred their consciousnesses into robotic bodies that resembled those of their culture's ancient deities made of the living metal called necrodermis. The matter around them was so insignificant that it did not register on their voracious appetite. After a time, they learned to use diaphanous wings to travel to other stars to continue their consumption when their host star died. In their natural form they are vast beings and spread themselves over the surface of a star, absorbing its solar energy to feed themselves. It is said that they were created at the very beginning of the universe, spawned from swirling gases and enormous amounts of energy, and as such are etheric creatures by nature. The C'tan (pronounced ker-TAN) or Star Gods, called Yngir in the Aeldari Lexicon, are said to be the oldest intelligent beings in existence in the Milky Way Galaxy. The necrodermis-sheathed C'tan Shard of Aza'gorod the Nightbringer in combat against the foes of the Necrons. From the Chronicle of Szarekh, Last of the Silent Kings Mephet'ran the Deceiver, Aza'gorod the Nightbringer, Iash'uddra the Endless Swarm I curse their names, and the names of all their malevolent brethren." " They came to us as gods and we, like fools, took them at their word.