Necros

"I've seen them, in the darkness, hiding between the stars. Hundreds, thousands of ships, a fleet of gibbering dead and machine. Repent! Repent now! Absolve your sins! When they come it will be to late! They will descend on this galaxy and strip it clean of all life. Nothing can stop them, they feed on the dead, swell their ranks from our own casualties, you have no chance! Ghosts of a hundred thousand years ago are coming to feed on this galaxy. Nothing will stop them, not the UNSC, not the Sangheili. Nothing will save us now."

- Ajax-013 upon being found in the hulk of the UNSC Aleous