Born the son of two exceptionally skilled Rangers, Klien and his twin sister Aelisia were destined to follow in their parents footsteps. At a young age they began their training, learning the art of combat in both marksmanship, swordsmanship, survival, and an educated understanding of strategy and tactics. Like many Rangers before them, they were quickly growing into a dangerous solider of Quel'thalas.
After their parents death, Klien and his sister began to work for a noble, a magister called Zhe'nergul. The aged wizard took on a tutoring role and helped the twins establish themselves in Silvermoon. They both grew close to him, and quickly adopted them as their mentor. With his help, the twins were able to reach their promotions to full-fledged Rangers in no time.
Still, after the Scourge attack on Quel'thalas he and Aelisia went their separate ways, with Klien leaving to join Kael'thas in his expedition to Outland, and his sister remaining behind in Silvermoon with Zhe'nergul. He was young, and hot blooded with a desire to avenge his people and the destruction of his homeland, ad so blindly devoted himself to his prince.
Klien witnessed Kael'thas' slow corruption by the demonic magic his people sought to control. He saw how twisted he had become, and the dark intents that began to fill his peoples hearts. Klien left with the Scryers to join them in Shattrath City when they defected from Kael'thas' rule. It was there that Klien would meet Skyguard Captain Nimraama Mallron, who he would latter marry and have a child with. Their daughter was named Valya Blacksun.
Klien would also reunite with his sister and Zhe'nergul after they had passed through the Dark Portal. Zhe’nergul gave Klien a gift in the form of a large Black Tome that would consume the essence of any demon slain by the wielder.
Klien used the book to slay hundreds of demons before joining the Shattered Sun Offensive. However, during the conflict on the Isle of Quel’Danas he was betrayed by Zhe’nergul, who had secretly aligned himself with the Burning Legion. He killed Aelisia and gravely injured Klien.
Using his political influence, Zhe'nergul declared Klien a traitor and accused him of Aelisia's death. News would later reach his wife that Klien had been killed. Truth was he was hiding out in Shadowmoon Valley, where he would remain in exile for over a year.
Klien would finally come out of hiding after hearing that Zhe’nergul would be attending the Argent Tournament in Icecrown. Klien took part in the games under a new identity so he could get close enough to Zhe’nergul. Though the warlock was powerful, Klien managed to defeat him. Zhe’nergul then exposed himself as member of the Burning Legion, and was quickly destroyed by Klien and other tournament participants.
