Prior to the creation of the League of Legends, the city-states of Demacia and Noxus were locked in a brutal series of on-again-off-again wars that spanned the course of centuries. Both powers sought an advantage over the other, but Noxus was the city-state willing to forego conventional morality to achieve its goals. Only brute strength and the will to use it mattered to Noxus, and this is best exemplified in the murderous warrior, Sion. Used by the Noxians as a human battering ram, Sion would be sent thundering ahead of Noxian troops. He would mercilessly slaughter foes with his large double-bladed axe, "Chopper". His complete disregard for caution ultimately cost him his life, as he was captured and summarily executed by Demacian forces.
The Demacians thought that the beheading of Sion would be the end of his bloodthirsty ways. Death, however, was merely the beginning of Sion's rise to power. The famed Noxian assassin, Katarina, recovered Sion's remains and Noxian necromancers reanimated the behemoth to serve Noxus once again. Sion's reanimation actually bestowed new powers on him and increased the potency of his existing abilities, making him even more of a terror to behold on the battlefield. The Noxian High Command had a powerful new weapon in their hands - one they have brought to bear as a champion in the League of Legends. Even though Sion's increased powers would make him a powerful tool for the High Command's use outside the Fields of Justice, Noxus no longer risks losing one of their greatest champions in the League to chance or circumstance; Sion's days as a front-line fighter for Noxus' military conquests are at an end.
"For Noxus, death is a promotion."