Unimon is a wise, old digimon that lives in the mountains of File Island. He tends to stay quiet and doesn’t usually interact with the other inhabitants of the island.
Joe Kido and Gomamon encountered Unimon on the side of a mountain path. They witnessed a Black Gear (in which it was revealed to be sent by Devimon) going into Unimon’s back and he attacked. He attacked Greymon and Birdramon before Joe tried to remove it himself. When he fell, Gomamon Digivolved to Ikkakumon and saved Joe and destroyed the Black Gear.