Ynnead

Ynnead is the Eldar God of the Dead.....or at least he will be, as he is currently being made. He is currently in godly limbo at the moment as the Eldar try to get enough pure souls or at least desireless souls together to give him enough mojo to form together into a proper god.

The whole process of god creation is a bit of a tricky one to explain but we'll try to keep it simple.

Basically, Ynnead is the Eldar's last hope against Slaanesh. When the bitch-goddess was born she devoured a lot of Eldar and their souls and most of their gods and basically caused a lot of things to get badly screwed up. To add further salt into the wound, the surviving Eldar found Slaanesh was constantly hungering for their souls, laying in wait for the moment an Eldar would die and then he would completely devour them. In the past the Eldar believed when they died, their soul would be reincarnated in a new life. With Slaanesh's coming though, the Eldar's ability to reincarnate disappeared.

To save them from this fate, the Craftworld Eldar use a spiritstone to trap their soul inside upon death. The spiritstone is then placed within the infinity circuit of the craftworld, where the soul is free to roam around and commingle with the other Eldar souls of the craftworld.

As more souls overtime have been added to the infinity circuits, the Eldar Farseers have perceived something stirring from this collection of souls; this is Ynnead, a god formed from untainted Eldar souls and the power of Asuryan, the king of the Eldar gods, who passed on his power to the Farseers of the Eldar before he was devoured by Slaanesh. The Farseers believe that when the last Craftworld Eldar dies, Ynnead will be fully born and will rise up to cast down Slaanesh, destroying him forever.

Whether this could be true or not, considering Slaanesh's immense power, is unknown, but Ynnead is the best hope of the Eldar for a better future for them and so all their efforts go towards making him as strong as possible.