Warning, spoilers below.
GW has decided to push further the lore in 999.M41 and the Eldar got a new faction with new rules after bringing a new(old) god into existence to fight Slaneesh... at the expense of fracturing the Biel tan craftworld into a fleet of spaceships.
Here's an account of what will be released on February in the Fracture of Biel Tan:
- The book starts in Commoragh - a shard of Ynnead (the Eldar god of the Dead) is there, Yvraine finds it.
- If there is too much psychic activity there - Slaanesh comes for you. So they are scared.
- Yvraine flees the city, gets saved by the Visarch - we don't know how he is.
- The Craftworlds are coming together. Eldar don't talk literally - the fracture is both the way what happens and what factions come out.
- Craftworlds weren't always one ship. Bigger than anything the imperium has, bigger than the Rock. Made up of different ships that are all stuck together.
- Biel-Tans infinity matrix has a fracture - there is a split.
- It's the kickstart Ynnead needs to get born. All the Eldar souls who are locked up there birth the new god. All the "parts" of Biel-Tan split up. It's basically a fleet now, instead of a craftworld.
- The Avatar is in the center of all the souls of eldar of Biel-Tan who died in the last 10k years. He is the proof that the prophecy of Ynnead is real. A beacon of hopes for all Eldar. They can now fight against Slaanesh.
- The Avatar is the mirror of Slaanesh - they are siblings. His power comes from Eldar souls - hence he looks quite Slaaneshi. They are made of the same stuff.
- Lots of interplay between the different Eldar factions in the book.
- When it's desperate, Eldar of all kind will fight against a common vow. Other times, they fight against each other, even Craftworlds vs Craftworlds.
- Now, the Eldar god of the dead is summoned - some see this as a hope for their race.
- These make up a new faction - basically the Eldar who believe in Ynnead. They have now a red colour scheme (like the Visarch, he is their leader). These are the Ynnari. Lead by the prophetess and the Visarch.
- Lots of wyches and Incubii.
- Some Eldar (of all kind) are very against this - especially the Haemoncolus Covens. They see this as "they steal our jobs". If there is a god of the dead - no slaves and stuff, so they are not happy.
- Clashes between the Haemoncolus Covens and the Ynnari.
- Part II is not a sequel - it happens at the same time of 'Fall of Cadia'.
- It ends at the same point as the first book.
- Rules to make the Ynnari. You can mix different Eldar races into one army now. They loose their army rules but gain instead a new special rule.
- Basically - when your eldar units die, your own units become more powerful.
- Ynnari are a whole new faction of the Eldar.
- Aeldari is the name for all Eldar.
- If you already got an army, you can decide to play it as Ynnari, but not all units can be taken. Most of the stuff can be used though.