User blog comment:RemosPendragon/Canon policy: Gods part 2½/@comment-25252114-20141123220551/@comment-8395098-20141124015441

Orriginal mythos the void dragon killed a lot of the other C'tan by himself in a hunger fueled fit....now that possition is a little questionable and it's uncertain if the Void Dragon whose imprisioned on Mars is THE full Void Dragon or just a shard (thanks WARD for ruining another part of necron lore)

The Nightbringer was just a Necron so closely related to death that his image imprinted into the psycie of most races as that of death.