A massive rule dump has been made. The translations for them are below, as well as the original text.
This all comes to us via Bell of Lost Souls from GW Fanworld
English Translation
via Norman Mach
The old placement of the army is gone.
No flyers, but flying MCs.
Demons belong to a god and have hatred to demons of an opposing god. Furthermore a Slaanesh Herald for example can't joint nurgle demons.
Khorne: Furios charge, HoW with chariot is S7
Tzeentch: +3 on Ld for casting PSI, reroll of failded inv. saves of 1
Nurgle: Shrouded, slow (don't remember the english rule name), every unit consisting just of Nurgle Demons counts equiped with defence grenade
Slaanesh: Rending and fleet, Slaanesh-only unit runs D6+3". Slaanesh cavallerie runs 6" more. Vehicles (no walker) move 3" more in the shooting phase.
Demonic Instability
Units with these rule can't be joined by a model without these role. Unit pass every Ld., pinning or fear test. If the demons are loosing a CC they must test with 2D6. The difference between mod. Ld and dice roll is the number of additional wounds without saves!
Double 1: Every lost wound in this phase is restored. Every removed model comes back.
Double 6: Remove the whole unit.
Warlord:
1) Every CC weapon of the warlord gains instant death.
2)Warlord and unit has hatred against everyone
3) As long as the WL is alive every enemy gets -1 for fear tests
4) Friendly units choosen from these codex in 12" of the WL can reroll failed demonic instability tests
5) As long as the WL is alive you can reroll every roll on the warpfire table
6) As long as the WL was on the table at the beginning of the turn, every unit with the rule demon (including from Codex: Chaos) coming via deepstrike won't scatter if the first model is placed in 6" of the WL
Warpfire table
Is only active when demons are the main army. Role 2D6 at the beginn of the demon shooting phase and apply the result.
2) Every unit with demonic inst. (friend and foe) has to test for it
3) Choose randomly one character with demonic inst. rule. Test with 3D6. Wounds can only applied to the character.
4) Every unit with demon gets -1 for inv. saves until next roll on the table
5) Roll 1D6 for every unit not in CC which contains at least one model with the sign(?) of nurgle or demon of nurgle. If you roll a six place the 5" template on the model of the unit and scatter as normal. S4 AP5 for friend and foe, ignores cover.
6) Like Nr. 5 just for Tzeentch. D6 hits with S4 AP3. Ingores cover, poison (4+), vehicles get a hit at side armour.
7) Nothing happens.
8) Roll one D6 for every Khorne unit or enemy unit not in CC. On a six - D6 hits with S6 AP-. Ignores cover and rending, vehicles get a hit on the side armour.
9) Roll one D6 for every Slaanesh unit or enemy unit not in CC. On a six - place 3" template. Every unit (friend and foe) gets one hit for every model with S8 AP 3. Count as barrage weapon.
10) Every demon gets +1 on the inv. save.
11) Choose random one enemy Psyker (no vehicle, no demon, must be on the table). Has to take Ld test with 3D6, if he fails, he will be removed. Place a new herald of your choice without upgrades within 6". Not allowed to charge.
12) Place instantly a new unit with 2D6+3 demons (Bloodletters, pink horrors, demonettes or plague bearers, your choice) via deep strike,
Demons have 6+ armour, some have better saves (blood demon has 3+).
Blood demon no eternal warrior. The skulltaker(?) has eternal warrior and 3+ armour. Skarbrand and Karanak don't have eternal warrior. Lord of Change is Mastery Lv. 2 (divination and change(?)) and flying MC.
11 to15 pink horrors generate two warppoints, 16 to 20 horrors three warppoints. Kairos has a 4+ inv. save. Each of Kairos heads is a Lv. 4 Psyker. Both heads knew every change spell. In addition gains the right head on power from pyro and one divination. Left head - one pyro and one telepathy. Have to decide which head you use these turn. Can reroll one D6 every player turn (even from 2D6 or 3D6).
The blue Tzeentch demons are no psykers, but can use one power from the rulebook rolled with the dice without psy test.
Changeling in basecontact can replace one his stats (WS, S, T, I and/ or A) with one the enemy.
Big plague demon has mastery lv. 1 and plague and biomanty.
Nurgle slime beast can charge in the enemy phase! Ku'Gath can give wounds back to Nurgle Swarms.
Epidemus and his special rule
Count every unsaved wound caused by a demon of nurgle (friend and foe). Count even lost wounds saved by fnp or reanimation protocolls. Every Nurgle unit in 6" of Epidemus gains following bonus (cumulative)
7+: +1 strength
14+: +1 toughness
21+: poison (2+)
28+: fnp (4+)
Keeper of secrets has prefered enemy Eldar/ Dark Eldar. Mastery Lv. 1 telepathy and Slaanesh party lore.
The mask can reroll every failed inv. save. Has different dance.
There are chaos furies (maybe chaos harpyies in english).
Flame weapon of tzeentch - SR warpflame. At the end of every phase a unit with an unsaved wound caused by it has to make a Toughness test. Fail - D3 more hits withour armour or cover, passed - gains fnp 6+. If the unit has already fnp it be better by +1.
A unit hit by a skullcannon can be charged withount Ini loss caused by difficult terrain.
Axe of Khorne: Instant death by a to wound roll of 6.
Mutated warpsword (Tzeentch) If the bearer kills an enemy Character or MC roll a D6. On a +2 it be replaced with a chaos spawn.
Warp...(Tzeentch): A character or MC killed by the staff of change will explode. Every unit in D6" will gain D6 S5 AP- hits.
Plagueweapon: Models with one unsaved wound caused by these weapon have to pass a Toughness test or will loose another wound (no armour or cover).
Sword (Slaanesh). Like plagueweapon, but with Ini test.
A lot of characters don't buy equiment. They buy gifts in three different levels for points. What exacly these gifts are will be choosen random (D6). Roll at the same time as for the Warlord trait. One model can't have a gift twice (reroll), but you can have a gift more than one time in your army. You can replace one of the gifts with the 0. You gain a weapon or artefact for it (just one example given in the german text - Blade with Ap2, mastercrafted and special weapon).
Skarbrand or Blood Demon make demon princes of Khorne to Heavy Support instead of HQ.
Kairos and Lord of Change do the same for Tzeentch.
Ku'Gath and Big Nurgle demon for Nurgle.
Lord of Secrets does it for Slaanesh.
Damonprince 145 points, has to choose one god:
Khorne 15p.
Tzeentch 25p.
Nurgle 15p.
Slaanesh 10p.
Can be a flying MC for 40 points.
Up to 50 points for gifts (Lv. 1 gift 10p. Lv. 2 20p. Lv. 3 30).
Demon Prince not can be a psyker (not Khorne)
Mastery Lv. 1 25p.
Lv. 2 50p.
Lv. 3 75p.
Heralds counts only as a half HQ choice. They have special presences. which can be upgraded and give the unit a bonus.
Icons can be upgraded for unique effects and instruments can get more units out of reserve and give you rerolls on the warpstorm table