The C'tan, also known as the Necron Star Gods or in the Eldar language, the Yngir, are a race of etheric creatures believed to be the first intelligent life in the Milky Way galaxy, created by Games Workshop as part of their Warhammer 40k series of miniatures. In their true form, they are immense energy creatures able to engulf entire stars. However, the Necrontyr created them physical bodies out of the living metal, Necrodermis, allowing them to interact with the physical world. Unlike the Chaos and Eldar gods, they hate the Warp and all psychic energies and have thus had the Necrons build a series of pylons across several worlds that, when powered, will close the Warp off completely, killing all living creatures with a soul. All C'tan are armed with special blades known as C'tan Phase Swords. Currently, only eight C'tan are known to exist: the Nightbringer, the Deciever, the Void Dragon, the Outsider, the Burning One, Kalugara, The Arisen and The Shaper. The rest were killed when the Eldar laughing god, Cegorach tricked them into devouring eachother.
The Nightbringer, known by the Necrons as Aza'gorod, is the Necron Star God of death, darkness and destruction. It has impressed its image as that of the Grim Reaper on the minds of all races in the galaxy, with the exception of the Orks, as they don't fear death. Upon entering stasis with the Necrons and the rest of the C'tan, it was starved and nearly dead. However, in the 41st Millenium, it was reawoken by Space Marines of the Ultramarines chapter, most of whom provided a fitting sacrifice to bring it to full strength and allowed it to reawaken most, if not all of the Necrons in the galaxy. It was almost killed when Captain Uriel Ventris of the Ultramarines threatened to bury it for another 50 million years upon its awakening, but managed to escape the orbital bombardment. The Nightbringer is one of the few C'tan to use a weapon that isn't a sword, instead using its own Phase Scythe instead. However, after its scythe was banished to the warp in a battle against the Old Ones who used to rule the galaxy, it has taken to using a blade.
The Deciever, known to the Necrons as Mephet'ran, is the C'tan of trickery, lies, manipulation and deception. It was because of the Deciever that the Necrontyr died out, replaced by the mechanical Necrons. The Deciever was shunned by its fellow C'tan long before the Necrontyr had even seen one. It was also the first C'tan to leave it's stasis tomb, remaining active in the Imperium of Man many years before the awakening of the Nightbringer.
Known as Mag'ladroth, the Void Dragon is the most powerful of the C'tan. It is widely believed that the Void Dragon is the Omnissiah that the tech-priests of the Adeptus Mechanicus pray to. This theory is reinforced by a suicide rush by five Shroud-class Necron cruisers, landing near the Noctis Labyrinth hidden under the surface. If the Void Dragon awakens, humanity will be doomed.
Tsara'noga, more commonly known as the Outsider, is the most mysterious of the C'tan. When the C'tan were tricked by Cegorach into devouring eachother, the Outsider was the only one who retained fragments of memory from those it killed. Driven insane by these voices, it went into exile, feasting on stars as the C'tan used to do. It is said to be the most dangerous and deadly of the C'tan, and it's rumoured that it is the driving force behind the Tyranids.
Known by the Necrons as Nyadra'zatha, the Burning One is the C'tan who showed the Necrons how to enter the Eldar Webway. As they lack psykers, the Necrons cannot travel through the Warp. However, thanks to the Dolmen Gates, they can now pass through the Webway. Like the Nightbringer, the Burning One uses a different weapon to the basic phase sword, prefering its eldritch flame that it desires to use against the Eldar, the greatest allies of the old one during the War in Heaven. Little else is known of this C'tan at the moment.