About the New Warp Rift

So, for those of you following along with the near constant drip of information pouring out of Games Workshop about 8th Edition, it won't have escaped your notice that the Galaxy Map has significantly changed since the last time we saw it.

Not only are there domains of the Necrons included in glorious detail for the first time alongside the (long-standing) Tau domains, but there is a giant Warp Rift that has split the Imperium in two as it streaks from the Eye of Terror to the Maelstrom and beyond. Moreover, there are new warp tears in most segmenta of the Galaxy. 

So what is the cause of these new Warp intrusions?

Of course, its a plot maguffin at some level. But what does it mean? Has the Emperor's will finally terminated somewhere and the light of the Astronomican failed? Has the ancient Eldar web way finally given up and daemons overran it? Or is it just that Chaos is generally rising everywhere?

To me, it is a little bit reminiscent of something out of Dungeons and Dragons. Go with me here.

In the Ravenloft setting, there were strong and significant changes to the map as the editions evolved. One of the most significant was the introduction of the "Shadow Rift" in the new arrangement of the domains of dread (it appeared in the book of the same name; the image shows its introduction). Basically: all the locations shifted around and a new dark realm erupted in the middle of the main map. It turned out to be a new "race" being introduced to the Ravenloft campaign (the shadow Fey). So do these new warp rifts in 8th represent the introduction of something even more malign in to the 40k universe? I don't think we're going to see the introduction of a new chaos power myself (unless there's a kind of Malal re-boot, or Slaanesh gets bested by the Ynnari or something), but hey, I've seen stranger and analogous things happen in other settings. And now I'm all curious about what it might all mean!