In the fictional universe of Warhammer 40,000, the C'tan originally lived as energy beings that fed on the stars themselves. They are also called star gods or star vampires. They were transferred to the physical world thanks to the technology of the Necrontyr.

The C'tan used the hatred of the Necrontyr towards the Old Ones to help them gather the more subtle living energy they now craved. The C'tan hate psykers (psychic telepathics who draw their power from the warp) and have thus set up a series of 'pylons' on Cadia, which, when completed, will close the Eye of Terror forever, thus blocking most psychic power.

In the war between the C'tan and their now slaves the Necrons against the Old Ones and the younger races their red harvests started to run dry the Laughing God tricked the C'tan into consuming each other until only 4 remained. Then a plague of Enslavers emerged which apart from destroying the Old Ones also depleted the red harvests further. Thus the C'tan decided to enter stasis until their harvests could begin again.

The 4 remaining C'tan are:

• The Nightbringer (almost destroyed and starved but was released accidently by Space Marines)
• The Deceiver (came out of Stasis an unknown time ago and has been weaving plots ever since, including the destruction of the Eldar weapons Talismans of Vaul designed to destroy the C'tan on their emergence)
• The Void Dragon (the most powerful C'tan, resides in Stasis on Mars and is rumoured to be the Machine god)
• The Outsider (A C'tan that went insane due to its comsumption of other C'tan, is currently imprisoned in a Dyson sphere under the Galactic plane)