Blackstone pylons have been mysterious objects, strewn around the Galaxy  in Warhammer 40k, but most notably, they were found on the fortress  world of Cadia before it fell. These monoliths seems to have some  purpose to the Necrons, weaken Chaos, and make the Aeldari a little  itchy. But what are these Pylons? What use did they have in a long  forgotten past? Could they seal the date of the Imperium of Man, leading  us to destruction? Or could they be the salvation that helps Guiliman  lead the crusade across the galaxy.