S02E47: BlackWarGreymon's Destiny

One of the children's Dark Spores blooms into a Dark Flower and is harvested by Oikawa, despite the DigiDestined's best efforts to stop him. When Cody's grandfather fails to dissuade him, BlackWarGreymon sacrifices himself to protect him. Noticing that Oikawa is possessed, he uses his remaining power to seal Highton View Terrace's portal to the Digital World.