Shenron is the Earth Dragon that has been there since the
early Dragon Ball series. He was created by the Kami that was Piccolo's good
half. He can grant one wish when the Dragon Balls are united and he is summoned.
However unlike Porunga, Shenron can't grant the same wish more than once,
so people can't be revived from death twice. This is the main reason they
go to Namek, so they can revive everyone using the Namek Dragon Balls. During
the Cell saga when Kami and Piccolo fused, the Dragon Balls disappeared, so
Dende was summoned from Namek to be the new Earth Guardian. Dende made a new
Shenron who could grant an extra wish.
