Saren, the eldest son of Aovin and Talris, died during the War of the Satyr.
Being surrounded, a group of night elves-druids sent the young Saren to warn the others about the scourge through the Emerald Dream. Alas, the satires overtook them too quickly, and the defenseless body of the elf was killed. Saren’s soul was saved from complete extinction (if I’m not mistaken, in “Stormrage” book the souls of people who fell into the Dream to fight Nightmare, after the loss of their bodies disappeared without a trace) by the green dragon named Isen. In gratitude and payment for his “salvation”, the elf could not visit world of the living, and instead was obliged to protect and care for the Emerald Dream for eternity.