Digimon Adventure

While traveling in the desert, Joe's Tag reacts, leading the group into a Roman-like coliseum. There, they are trapped by Etemon, and Greymon is forced to fight another Greymon. After Joe finds his Crest of Reliability, the group escapes. Tai attempts to force Greymon to digivolve. Greymon digivolves into SkullGreymon and loses control of himself—attacking the others who are unable to stop him. SkullGreymon eventually reverts back to Koromon and apologizes for his behavior.