Darkness In His Heart

When on a trip to the mountains, the ninja are attacked by a mysterious figure, injuring Kai and Jay, while the figure infects Cole's heart with darkness. Afraid he'll hurt the ones he loves, Cole flees, vowing only to return once his darkness is under control. A year later, New Ninjago City is under attack, the ninja captured, now it's up to Cole to save them, using his new powers