From the introduction:
Welcome jumper, to the world of Xiaolin Showdown. 1500 years ago a grand master in Xiaolin magic, Shen Gong Wu, and martial arts sealed away a great and powerful Heylin witch by the name of Wuya. While he could not kill her, he did manage to seal her away in a box. After this he went and hid his creations, the Shen Gong Wu across the world with his dragon, Dojo. You start in the beginning of the show, right after the genius criminal, Jack Spicer frees Wuya from her imprisonment. While she is currently weak, she has influence over the boy, and as such is still a threat. Meanwhile, an orphan by the name of Omi is being raised by a practice of Xiaolin martial arts by the only remaining teacher, Master Fung.