Morro knows he's destine to be the Green Ninja. Wu is wrong about him. Morro is now going out, alone, to prove that he is worthy of being the Green Ninja and worthy of being around.
A ghost escaped the Cursed Realm and it's now possessed Lloyd. That ghost was Morro, the former Master of Wind. Now it was up to the ninja and Tina to save Lloyd and stop Morro. Or else the world will be cursed.