Long ago in the vastness of space, a great, formless, mindless entity of evil arose. Before it could do harm to the universe, it was set upon by three deities, each one originating from Norse, Egyptian, and Hindu mythologies: Odin (the father of Thor), Ra (the Sun God), and Rama (the seventh avatar of Vishnu the preserver). The three deities fought a fierce battle against the black mass and burned the entity almost completely out of existence with their divine power. However, during the battle, one small fragment of the entity was incidentally cut from the whole by Odin and was never burned away.

Unnoticed by the three deities, that seemingly small fragment floated away from the site of the battle and drifted through space for an untold amount of time, until it eventually, and violently, crashed on Earth during the Cretaceous Period in the Mesozoic Era. It was implied that the fragment of the black mass is the very object that caused the extinction of the dinosaurs, although the crash occurred in prehistoric Japan as opposed to the Yucatán Peninsula by a massive asteroid.

Over eons, the fragment evolved into an ever-growing ominous forest of black tree-like spikes, which surrounded a tar-like pit at its center, that devoured any living thing that dared to enter. Eventually, the forest grew so large that The Emperor (Jack's father) decided to kill the evil at its source. After he was armed with a poison elixir that was given to him by a Buddhist Monk, the Emperor, with his cavalry, rode into the forest. As they rode, the forest began to gradually kill off the Emperor's men and left the Emperor himself as the only survivor. Once he arrived at a black lake in the forest's center, the Emperor doused one of his arrows into the elixir that he was given and fired it into the black lake, with him believing that it would destroy the evil forest.

Unexpectedly, the poison arrow's magic had the unforeseen effect of galvanizing the evil mass into a humanoid form: it gave it intelligence, sentience, and shape-shifting abilities. This entity proclaimed itself with the name of Aku and thanked the Emperor for inadvertently helping him. The Emperor then attacked Aku, but with nothing more than his mundane and mortal weapons, he couldn't inflict any harm upon Aku. Aku then easily defeated the Emperor and strapped him to the side of a tree so that he could watch as Aku began destroying his kingdom and slaughtering his people.