NECRON ARMY-WIDE SPECIAL RULES
• We'll Be Back from the previous codex has been replaced by Reanimation Protocols (sorry I keep accidentally calling it Resurrection Protocols in some of these teasers). It now works at the end of each phase, but only on a 5+. You now remove models and place a token or marker next to the unit to remind you how many rolls to make (although you could just use the downed models as markers, but the important thing is you know that these markers don't affect gameplay at all). The rules are very clear about when/how models that return to play via RP are placed and if the entire unit is wiped out then the unit is gone and now RP rolls can be taken. Similarly, if the only model left in the unit is a character (such as a joined IC or a Cryptek/Lord) then these models alone are not sufficient to allow the other models to attempt their RP rolls. Nearly every non-vehicle unit in the game benefits from RP (as opposed to the old WBB, which only worked for 'Necrons'), except for the C'Tan shards.
Reanimation Protocols returns the model to play with a single wound unless they have a Phylactery in which case they come back (the first time they get back up) with D3 wounds.
• Ever-Living. This is basically just an additional Reanimation Protocol rule that characters have to describe how they're placed back on the table. Only characters (including basic Lords & Crypteks) have this rule, no squads do. The only real thing to note about it is that if the model wasn't joined to a unit when it went down, then if it returns to play it must be placed within 3" of the spot it fell. So characters are the only models it really matters where their 'marker' is placed when they are removed. So in some situations, such as an enemy unit killing a character with Ever-Living in CC and then consolidating on top of his marker, it would be entirely possible to prevent him from returning to play (as they can't if you are unable to place them within 3" of the spot they went down).
• Entropic Strike. This is mainly a Scarab rule, but it also applies to a few close combat weapons in the army as well. Basically if a model suffers an unsaved wound from an Entropic weapon then it has it armor save immediately changed to '-'. Obviously this would only apply to multi-wound models as any other type of model would be dead if it suffered an unsaved wound (ignoring the argument about whether a wound stopped by 'Feel No Pain' still counts as an unsaved Wound or not). Against vehicles, for each hit by this weapon type means at the end of the phase you roll a D6 and on a 4+ the vehicle's armor value is reduced by '1' on all facings. If a vehicle is reduced to '0' on any facing then it becomes wrecked immediately.
• Living-Metal. Not just for the Monolith anymore! Many vehicles in the codex have this and it basically allows the vehicle to ignore a Shaken result on a 2+ and a Stunned result on a 4+. These rolls are made immediately when the vehicle is damaged so this is nowhere near as good as the Grey Knights ability to remove Shaken/Stunned results.
• Phase out is gone (good riddance, I say ).
• There doesn't appear to be any Force Org shifting around in this codex at all unlike most other recent codexes (so taking any special character doesn't allow you to take a unit in a different section of the Force Org chart at all).
NECRON ARMY-WIDE WEAPON NOTES
• Gauss Weaponry does NOT have rending. It retains the 'auto-glance' on a penetration roll of a '6' rule, but has otherwise has lost the 'auto-wound' on a roll of a '6' regardless of Toughness that it used to have. The Gauss Cannon is now apparently Assault 2 & AP3 (I'm assuming the Strength is still 6).
• Telsa Weapons. With these weapons for every '6' rolled to hit the 'target suffers 2 additional automatic hits'. Whether or not that means the target suffers 2 or 3 hits in this case is a bit ambiguous, but I think the word 'additional' means that its actually 3 (one for the original hit for rolling the '6' to hit and then another additional two for a grand total of 3). The big daddy version of this weapon found on a lot of the heavier vehicles is the Tesla Destructor (and is almost always twin-linked to really maximize the chance to get those extra '6's to hit). All Tesla weapons are 24" and AP '-', but the Destructor is S7, Assault 4 and 'Arc' (which means you roll a D6 each unit, friendly and enemy, within 6" of your target and on a '6' they are struck with D6 S5 AP- hits as well). While the AP '-' keeps this weapon from being a premiere light vehicle killer, I think with all the potential S7 shots this can theoretically kick out, it still going to be pretty good at zapping vehicles.
The weapons go in order from lightest to heaviest as: Tesla Carbine -> Cannon -> Destructor.
• Particle Weapons. These are basically the blast weapons of the Necron army (with the exception of the pistol variant) with no special rules. They all have a pretty high Strength and a mid-range AP.
The weapons go in order from lightest to heaviest as: Particle Caster (pistol) -> Beamer -> Shredder -> Whip.
• There aren't any weapons that ignore invulnerable saves in the codex either...however there are quite a few little special abilities scattered about that simply remove models from play if they fail a certain kind of test, which does effectively ignore invulnerable saves (and any other kind of save too).
New Necron Fluff
NOTES ON NEW NECRON FLUFF
There is a dramatic change in the fluff in this codex from the previous incarnation of the Necrons. The Necrontyr's empire was massive at one point, but the different Lords in the empire started to turn against each other in civil war. To prevent this from happening the overall ruler of the Necrons (the Silent King) started the war against the Old Ones specifically to give them a common enemy to fight against to prevent his empire from destroying itself. Of course, the Old Ones ended up kicking their butts and in desperation, the Silent King found the C'Tan and agreed to the Deceiver's pact without realizing what he was doing. However, after the Necrons helped the C'Tan to kill off the last Old Ones, the Silent King then ordered the Necrons to turn on the C'Tan in vengeance and utterly destroyed the C'Tan into tiny shards. This war agains the C'Tan weakened the Necrons overall so much they decided to go into stasis to avoid the vengeance of the Eldar (the C'Tan had killed the Old Ones, but not all their children).
Now that the Necrons have reawakened in the 41st millennium, their goal is no longer to 'harvest' souls for the C'Tan (the C'Tan shards are now their slaves) as it was in the old book, but rather to reestablish the great Necron empire that spanned the galaxy before the war with the Old Ones began. However, the overall hierarchy of the Necron people is gone for the most part, leaving each individual Empire to once again rule for itself. This means each Tomb World (or cluster of Necron worlds) is essentially a separate little empire to itself, with a full backstory and idiosyncrasies. While Necron warriors are pretty much just automatons and Immortals not too much better, every other higher Necron being is now much more like an actual person, as their essence is simply trapped inside a metal body.
So there is lots of crazy nuance to Necron culture that was never present before. The codex now has plenty of 'quote' boxes featuring memorable quotes from Necron Lords like other races have in their books. There are some Necron Lords who honor valor in battle, there are a few Necron Lords who trade with other races, and although an uneasy alliance apparently, yes Necrons and Blood Angels did end up fighting against a Tyranid Hive Fleet together. Oh, and there is definitely plenty of reason to have Necron vs. Necron action now (as the old feuds between competing Necron Lords flare back up again).
All in all, it is a major tonal shift. While part of me recoils from it, the other part of me thinks that Necrons as they were had no distinct 'character' that each player could choose to get behind. Yes, the race as a whole had 'character' in how it was organized and functioned, but there was never any really good reason that a player should have his Necron force painted and modeled 'X' way as opposed to another player with his Necron army looking 'Y' way. People certainly painted their Necrons in different (neat) ways, but there was never really any good fluff giving players inspiration to do so.
The only real 'personality' in the old book was the Deceiver, and that frankly wasn't the Necrons, it was their god. The mindless mission that all Necrons were on was basically really similar to Tyranids...the Necrons were coming to harvest every living thing in the galaxy (yawn).
This new incarnation, love it or hate it, gives the Necrons a whole wide array of personality and every single empire has different goals and motives (not to mention paint schemes, markings, etc). Some Necron Lords are obsessed with finding the perfect flesh bodies to transfer their sentience back into. One Necron Tomb World was damaged during the great sleep and erased all the Necron sentience and has started basically commanding its Necrons like true robots (and is actively attacking other Necron worlds to take them over and keep growing), and there are of course dozens more little stories. The Silent King, who put himself into exile (for his unforgivable crime against his people) by leaving the galaxy after defeating the C'Tan encountered the Tyranids in the void between galaxies and has returned to spur the Necrons into action against the Tyranids (realizing that if the Tyranids wipe the galaxy clean of biological matter, then the Necrons will never find a form to transfer their minds back into).
Oh, and the biggest rival of the Necrons is now actually the Altaoic (sp?) Craftworld. Apparently they are the only Eldar who stayed true on the original path to seek out and destroy Necron Tomb Worlds while the rest of the Eldar got all caught up and destroyed in their decadence and then the Fall. Altaoic rangers have traveled the galaxy far and wide over the millennia (ever since the Necrons went to sleep) to track down and destroy or hamper Tomb Worlds from reawakening.
So with this new direction there is now tons of different possibilities for players to make Necrons forces different from each other and there are neat new takes on 'nemesis' races like Eldar & Tyranids to drive gaming plots as well as good reason for Necron on Necron battles.
And as for totally destroying the background of the C'Tan, the codex does allude to the fact that there are lots of unaccounted for C'Tan shards still allegedly cast around the galaxy. The Necron are always trying to hunt them down and imprison them (in pocket dimension prisons), but this does still leave the door totally wide open for a shard of 'The Dragon' to be on Mars and for shards of 'The Deceiver' to have done all the crazy things that's been written about him in novels. Essentially, the full power C'Tan were massively, massively powerful, and the 'shard' versions of them are closer to the idea of what we had in the last codex anyway (something that can be killed/banished on a battlefield).
So while it is a little shocking to have such a massive fluff change hit, I do think it is probably the right way forward to create a more fully realized faction. But I do think it is probably going to be a massive turn-off to those players who absolutely adored the old fluff for the army.
Regarding the previous fluff saying that Necrons went into hibernation due to a massive 'Enslavers' invasion, in the new fluff they only really briefly mention that the wars unleashed some nasty things from the Warp, but they literally do not mention the Enslavers anymore. It is very clear that the Eldar empire is the main reason they go into hibernation, having some sort of premonition that the Eldar can and will eventually crumble as all living beings and empires do.
It was a fairly solid plan, except a lot can go wrong when you're sleeping for 60 million years, and apparently billions of Necrons have been killed by simple, normal shifts in the galaxy in that time (stars going supernova, tectonics crushing tombs, etc)...but what they didn't predict was how poorly they'd all awake from the sleep. All Necrons were supposed to wake up at once, but that didn't happen. Some Necrons woke up during all periods of history (including the Horus Heresy) and many still haven't woken up. And in some cases those that wake up have suffered terrible afflictions (like the Flayer disease).
Since there are any number of strange and undocumented Tomb Worlds now, there is totally space for you to come up with whatever backstory and motivations you want for your personal Tomb World, much like every other codex allows players. Of course, there are also dozens of tiny little story snippets (as there are in every new codex) that give you plenty of inspiration to create and play armies as well. For example, say you really like the whole 'automaton' feeling the army had in the old codex. Well, in the codex they have a story telling of one Tomb World that during hibernation accidentally erased all the sentience from the sleeping Necrons and decided to 'take them over' and has since decided this is the way forward for the Necron race and is actively attacking other Necron Tomb Worlds to collect more bodies for the cause. Basically the only sentient brain in that whole army is the Tomb World itself (it even has given itself a name). So you could definitely use this backstory as 'your' Necron force and stick with more of a simple, robotic feel to your army.
Bits of the fluff talk about other races & systems paying 'tribute' to the Necrons...here's my speculation based on what I read:
Necrons have always felt like they got the short end of the stick. When they were Necrontyr, they had a crappy planet and that drove them to invent technology and get the hell off their planet...but they still wanted to prove they were the best so they set about trying to creat the greatest galactic empire. And they did...but then as always happens, their empire started to creak and moan, so the war against the Old Ones started with naturally the belief that the Necrontyr would destroy the Old Ones and emerge even greater than before, the true heirs to the galaxy. And in fact they hated the Old Ones if for no other reason than because they had the secret for immortality (what the Necrontyr wanted more than anything) but wouldn't share it. And once the war started, naturally the Necrontyr couldn't beat the Old Ones despite their superior technology, as the Old Ones had access to the Webway which meant they could escape anytime they needed.
So eventually the Old Ones (and the races they created) were kicking the crap out of the Necrontyr. And so in the frustration of again getting the short end of the stick, they made the pact wit the Deceiver and sold their souls for immortality and power. But again, they felt shafted because they had essentially been tricked into doing this. So after the C'Tan had killed the Old Ones, they again wanted to take their rightful place as rules of the galaxy but they knew that would never happen as long as they were slaves to the C'Tan, so they turned on them as this is the only way they'd ever be free.
But of course that battle against the C'Tan did tremendous damage to them and thus they decided to use their immortality to 'outlast' the Eldar empire (which they did).
So now that they're back awake (mostly), although they've lost their main command structure as a people that sort of drove them forward towards any single goal, I think their goal is still to do what they always wanted...to rule the galaxy, to be the supreme beings. And this isn't exactly the same as humans, who basically want to eradicate all Xenos and populate all the planets themselves. Necrons more than anything (I think) want to be in control. They want to be worshipped by others. They finally want to get their due as being the rulers. So while they most certainly plan to destroy any force that gets in their way, I also get the distinct feeling from the new fluff that (with at least some of the Lords) they are perfectly okay with leaving existing planets/systems under alien control, as long as those people pay them tribute. Even though I have a hard time imagining what tribute the Necrons would really need (being robots and all), I don't think that's the point. The point is that the other races are paying them fealty and recognizing the mastery of the Necrons, which is precisely what they've always wanted.
As said before please take with a pinch until we get the codex.