Necrons

The Necrons are a mysterious race of robotic skeletal warriors

Basic Facts
They have lain dormant in their stasis-tombs for more than 60 million Terran years and who are the soulless creations and former servants of the ancient C'tan, the terrible Star Gods of Aeldari myth.

The Necrons are ancient beyond reckoning, predating even the birth of the Aeldari. At long last, however, they are beginning to awaken from their Tomb Worlds, for the galaxy is ripe for conquest and the restoration of the Necron Empire since the disappearance of the Old Ones more than 60 million standard years ago.

With the disappearance of the old ones before humanity flourished, the necrons ruled the stars.