The C'tan

The C'tan, sometimes called the Star Gods, were beings of pure energy that fed upon the life of stars in the galaxy's distant youth. Vast, immortal, and utterly alien, they existed as immaterial essences within the hearts of suns until a fateful bargain drew them down into physical form.

That bargain was struck with the Necrontyr, a dying race who, in their war against the Old Ones, forged bodies of living metal for the C'tan to inhabit. Clothed in these necrodermis shells, the Star Gods discovered a new and terrible hunger, feeding no longer on stars but on the life-energy of living beings. They led their Necrontyr servants, now transformed into the undying Necrons, to catastrophic victory in the War in Heaven.

The C'tan's tyranny did not last. Fearful of their monstrous masters, the Necrons eventually turned upon the Star Gods and shattered them into countless fragments, binding these C'tan Shards into servitude. Now the shards are wielded as living weapons of incomprehensible power by their former slaves, unleashed only in moments of dire need. Diminished though they are, even a splinter of a C'tan remains among the most dangerous entities in existence, a caged god nursing an eternity of hatred. For the fuller tale, see the Necrons and the Silent King.