Dion is a character from the alternate "Dragon Ball Time Bend" universe.
In the year 1801, the Saiyan race was gone. The attack of the Shadow Dragons had forced Goku and Vegeta to self-destruct to save the Earth and the universe at large, and the human population was reduced by 98%. Among the few survivors were Krillin, Tien Shinhan, Pan, and Pan's young daughter, Dion.
Unfortunately though, it was only a few years after Goku and Vegeta "defeated" Omega Shenron that he revealed himself once again, having survived their self-destructive attack!
Because that technique literally never works. Either way, it did enough damage to force Shenron to spend years in hibernation, regenerating from a few clusters of cells.