In a nutshell, the Necrons are Egyptian-looking cybernetic beings who once ruled the galaxy lifetimes ago. They have slumbered for millennia and have only recently awakened to a galaxy at war.
In their leaders’ pursuit to achieve immortality a bargain was struck with god-like beings called the C’Tan. Unfortunately their path to immortality was in the form of a mass conversion of their entire race into their current forms.
For a time they remained enslaved by the C’Tan but they eventually overthrew their god-like overlords. The Necrons in turn enslaved their cruel masters; harnessing them as a source of energy. Take that you C’Tan cheats!

With this new found power the Necrons proceeded to conquer world after world; forming an empire and becoming rulers of the galaxy. What happened to them next? Why did they disappear for millenia? Why are the awakening?
I’ll write more about the Necrons in future instalments once I get more comfortable writing little articles like this as I fine-tune my content format. Till next time!