S02.E19 Tale of the Demon Tail / Demon in Di-Skies

The Dark Hand manage to release Hsi Wu, a demon with dominion over the sky, from his portal at Fenway Park, before the Chans can send him back through it. However, in his attempt to escape, Hsi Wu loses his tail in a freak accident, to which Uncle seals it behind chi magic until he can use it to locate him. To restore himself, the demon disguises himself as a human boy in order to win over Jade and steal back his tail. When Jade discovers his deception, she soon seeks revenge on Hsi Wu when Uncle is kidnapped by the demon.