-Sisters of Silence may officially be gone. Black Ships are described as being crewed by Adepts of the Adeptus Telepathica with Inquistors as captains.
-The Iron Men and their war are alluded to, stating that during the Age of Technology mankind relied heavily on robots. Short before the Age of Strife they rebelled, and a massive war took place that saw such devastation that it helped herald in the Age of Strife
-The largest Ork Waaagh!'s the Galaxy has ever seen took place shortly before the Horus Heresy. They seem to make current Waaagh!'s seem like picnics. Horus' role in defeating them is what earned him the title Warmaster
-The Inquisition still retains the 3 classic Ordo Militants it seems. It is flatly said that the Grey Knights are the Ordo Militant of the Ordo Malleus, the Deathwatch Ordo Xenos, while the SoB maintain "close ties" with the Ordo Hereticus. The SoB don't seem to be formally an Ordo Militant but a de facto one.
-The Tau-Ultramarines alliance or Tau ties to the Emperor is never alluded to. Beyond the Allied chart there's no explanation why the Astartes and Tau are brothers in arms.
-The excerpt about the Golden Throne malfunctioning is in there, but it's the exact same one from 5th Edition. No progress. The only new bit of info really is that the Golden Throne requires far more psyker sacrifices than it used to, about four times the original level.
-There's a new ship called the "Blade of Eternity" that was lost in the Warp over 20,000 years ago and seems to appear again before any major Chaos incursion.
-In M39, 5 great heroes returned that are comparable to the Primarchs. They do a bunch of great stuff and oversee a bunch of great victories but vanish suddenly vanish.
-A major war against the Hrud occurred in M35, the "Hrud Rising". If GW is ever going to add another Xenos race (unlikely), but guess is it'll be Hrud by this point.
-In late M41, much of Segmentum Pacificus is in full-fledged rebellion
-The Adeptus Mechanicus is no longer part of the Adeptus Terra. It is separate and reports directly to the High Lords of Terra, like the Ecclesiarchy.
-During the Dark Age of Technology, mankind went on an alien-extermination campaign. Many xenos species were wiped out and their worlds colonized by humanity. Humanity had some sort of relations with the Eldar during this time, and also mentioned Orks (undoubtedly meaning wars with them). Today, often invasions by lesser alien races on "Imperial" worlds are just attempts to reclaim their lost homelands
-A few new Xenos seem to be mentioned. The Zygo live on Camgia have successfully fought off Imperial invasions for the last 500 years, The Dracolith, an emerging alien empire mentioned in 5th edition, are described as being chrystalline beings. There's a big picture with an illustrtion of lots of interesting-looking minor Xenos races. However none are identified by name. Frustrating.
-At one point, an Ork Warboss known as "The Beast" seemed to have united the Ork race (or at least most of it) and nearly took over the galaxy in an "apocalyptic greenskin uprising". This was during the Age of Imperium and is described as one of its darkest hours.
-Dark Eldar don't just seem to not use Farseers and Warlocks and what have you, they are stated to not be psychic altogether. No explanation as to how this difference from Craftworld Eldar took place.
-Tyranid Hive Fleets encountered are described as consisting of millions of Bio-ships each with millions of Tyranids on board. So it seems that Hive Fleets can easily approach the trillions figure in size.
-Tyranids fight with each other now. Hive Fleets compete with each other and clash over food on planets. The Hive Mind is still stated to be directing the overall Tyranid race regardless of this, this is probably the stupidest thing in the Codex.
-The Tyranid Hive Fleets seen so far are just a splinter of the 1 furthest tendril of the main Tyranid invasion force in the galactic void.
-The section on Chaos is entitled "The Greatest Threat". They get a lot of fluff dedicated to them, Chaos as a whole has a level of fluff coverage (almost 20 pages) only the Imperium surpasses in page amount. Hyperbole, or is GW making Chaos out to be the big baddie again? With downgrading the Tyranids to fighting one another, who knows.
-Chaos is definetly displayed in a more united fashion of CSM, Daemons, and heretics working towards a common goal. CSM/Daemon/Cultist fluff is all intermingled together and their models showcase are intertwined together under the title "The Great Enemy"
-Non-Marine Chaos followers have their own section of fluff (though it says what we already know), preparation for GW to give the Lost and the Damned a greater role in the future perhaps.
-The actions of the battles between the 4 Chaos Gods in the Warp directly effects the Materium in a more material fashion. For instance, if Nurgle is doing well in the war before he is inevitably pushed back, there will be rampant plague in the galaxy.
-A funny tidbit about Alpha Legion taking over Imperial communications outposts and sending false reports for decades at a time (not relevant, just found it funny...)
-Abaddon's Black Crusades are described more as repeated blows to the Imperium to gradually weaken it and as part of a greater plan, rather then 13 separate attempts to march on Terra. None of the Black Crusades are described even as failures. GW trying to end the stereotype of Faildabbon I take it.
On a separate note, the Dark Angels seem to take center stage here. They have cover art, back art, and the intro art for the Space Marine section.
