Kame is Earth's god in the first part of the DBZ series and he is later replaced and merged with a new Namek named Dende. Kame and Piccolo are part of the same life-force, so if one of the dies so will the other. When Piccolo dies while saving Gohan, Kame goes with him to the next dimension. Kame is not really a fighter, but he will protect the Earth if need be.