Valheru, also called The Dragon Lords, were the first race on Midkemia, and among the most powerful in the known universe. They rode on the backs of great dragons, travelling throughout the cosmos in search of plunder, and proved superior to all other races and cultures which they met and destroyed - some of these being themselves highly technological interstellar empires. Arrogantly presuming themselves to be gods, they also created lesser races to serve as slaves.
As a result of their wanton acts of destruction throughout the universe, energy was released from what were once mighty civilizations. Reaching a critical point, these energies formed a new pantheon of gods. While the new gods strove among themselves, the Valheru, exhorted by Draken-Korin, attempted to overthrow the new order of gods.
Ashen-Shugar was the only Dragon Lord to disapprove of his son's plan, but he did nothing but watch as the other Dragon Lords rose to battle the gods. Ashen-Shugar, the most powerful of the Valheru, felt something "alien" to his kind, a desire to protect the world, and the presence of Tomas via the magics of Macros the Black. With the coming of the new gods Ashen Shugar felt himself become alien to the new order, as if reality rejected his nature and he fell into a torpor, sleeping in his mountain on his throne many ages after the rest of the Valheru had gone away. Upon his death his essence became infused in his armor so that Tomas could replace him as guardian of Midkemia.
Space and time became warped as the Valheru battled the gods in the time known as the Chaos Wars. Of one hundred gods, only sixteen survived, but the Valheru were defeated. With the exception of Ashen-Shugar, the Valheru were cast away into another dimension to prevent them from returning to their homeworld, Midkemia.
In A Darkness at Sethanon the Valheru briefly returned to Midkemia at the end of the book, Draken-Koren and Tomas/Ashen-Shugar fought and Tomas impaled Draken-Korin to the Lifestone, and the Lifestone sealed the Valheru in it and prevented the end of Midkemia. Tomas's blade was left in the Lifestone for 50 years until Rage of a Demon King.
In Rage of a Demon King, Pug, Miranda, Nakor, Tomas and Calis, along with Brother Dominic of the Priesthood of Ishap and Sho Pi (a former Monk of Dala and, until near the end of Shards of a Broken Crown, Nakor's disciple), went to Sethanon to the Lifestone. Calis, being human, elven and Valheru, managed to undo the Lifestone over a period of many hours and amidst a battle with Jakan, a demon who sought the Lifestone for his own selfish gain. After defeating Jakan, the Lifestone (Which had the Valheru trapped inside) was destroyed forever, and with it the Valheru. Calis and Tomas/Ashen-Shugar suffer a painful transformation as this occurs, as their Valheru parts are "returned to the world", but being "more than Valheru", they survive.