Arium the Eternal was the final emperor of the Old Empire, and was assassinated by Zen Lobo, a follower of Domecus. He died in his personal chambers of a heart attack brought on by the assassin, and passed away peacefully, reassured that he would be reincarnated. His Empire was subsequently dismantled by the followers of Domecus and eventually was completely obliterated. It didn't see a resurrection until the Foundation years later, and that too was destroyed by the Domecus followers before it could consolidate enough power to be long lasting.
While he was the incumbent emperor, he had a tower built in the south of the Crownlands called the Eternal Obelisk to commemorate his legacy. It later became known as the Silent Tower after the Empire fell, and much later became the Wilderman's hideout, the Heibach Mire.
Emperor Arium was an obsessive researcher of one of the Four Divines, Logos. Logos is the deity which governs all life and nature, and Arium postulated that people could be reincarnated after death as a plant, animal or even another humanoid. His research and beliefs on reincarnation survived despite his own death, and after the Old Empire fell, proponents of his theories were among the founders of Moray (sans Taog Tulach, its first leader). These proponents created the College of Moray where Ariums philosophy was taught as a martial and moral code known as the Denmer Code. However, due to pressure from skepticism (which was largely influenced in secret by the followers of Domecus who wanted to suppress knowledge of the Four Divines), the College was closed and the followers of the Denmer Code were scattered, the code itself declared illegal by those in charge of Moray.
Place of Origin: The Great Empire