Aum

Aum is the proto-Ettin from whom all Ettin and deities are descended.  However, the Eldar believe was Aum was a created being and not the first thing to emerge from the void of chaos. Aum was a hermaprhoditic giant who emerged from the collision of the early forces in the void. Some Eldar believe Aum was created by the Creator who is outside of space and time.  In any case, Aum was directly or indirectly responsible for the creation of much of the known world and its species.  
The body of Aum was desecrated by the brothers Imir, Fel, and Delon when they murdered them and torn them apart. The ground up bones of Aum were used to seed the mountains which still grow towards the stars. The eyes of Aum were burned and scattered throughout the universe and have become stars.  The blood of Aum fills the rivers and lakes of the world and is the reason fresh water is nourishing while salt water cannot be used for drinking.