During the chaos of the Rune Wars, an enormous runestone was lost deep within the Plague Jungles. It remained there, untouched for centuries, emanating a potent magic which infused nearby wildlife with sentience and vitality. A group of monkeys who were particularly empowered by it came to worship the stone, and their leader - a wise sage - became convinced that he could harness its power to make the monkeys immortal. He performed an elaborate ritual, but things didn't go as he expected. The runestone was destroyed, and instead of granting immortality, it produced Kong, a monkey who carried in his heart the strength and power it had contained. Kong was driven by an unquenchable desire for greatness. He sought out every beast and monster the Plague Jungles could offer, eager to find a worthy opponent, but none offered the challenge he craved. He asked the sage for advice, and learned about a legend of hairless monkeys to the north who, with wits and might, had bent the world to their will.
Kong left, journeying north, determined to discover if the legend was true. He crossed the Southern Wastes and then the Great Barrier. On his way, he happened upon Master Yi, who was deep in meditation. Kong asked him who the strongest warrior in the north was, and Yi told him about the League of Legends. The tale intoxicated Kong, a place where he could battle the strongest fighters in the world was, to him, paradise. Kong asked Yi to introduce him to this League, and to teach him the ways of humans, so that he could be a fitting champion. In return, he would honor Yi by using Yi's Wuju style to become the greatest warrior Runeterra had ever seen. Admiring his passion, Yi agreed, but under the condition that Kong would one day teach the lessons of Wuju to a pupil of his own. In the spirit of this agreement, he renamed Kong Wukong, and gave him a weapon suited to his unusual nature - an enchanted staff that the young Doran had crafted. The weapon was an unrivalled masterpiece. Guided by Yi, Wukong joined the League of Legends to prove himself as the best, and to show the world the true power of Wuju.
Source: The Publisher Website.