Brightbane

'The essence of Divinity' - in the form of a unique metal

Ygdrassil 'feeds' on Brightbane

Brightbane represents the raw energy of the souls of the dead. Ygdrsassil draws it up from the underworld and delivers it to the gods in the heavens (outer planes). This is why it was historically never seen on Prime, it was all being channelled to the Gods, who drew their divine power from it. The En is now diverting Brightbane away from it's natural course, preventing the Ragnarok cycle from being completed through the creation of new Gods. Instead they seek to use it for their own purposes, including a path to forced divinity for some (like Yenoghu). There is a connection/similarity between brightbane and water - the metal flows like water and it is the raw essence of life for the gods in the same way as water is for mortal beings on the Prime. Moreover, it's path is being diverted to serve the enemy in just the same way as they are diverting water on the Prime.

There seems to be some connection between Orodruin and Brightbane - this may be linked to the fact that he lives in Limbo, where a powerful enough will can create anything.