What is "Majin" you ask? Well majin is what the evil wizard bibidi was. He was the evil wizard that created the evil majin buu with hopes to take over the universe with his evil creation. His plans failed obviously if you have seen any of the newer dbz episodes. But in the newer episodes of DBZ, Bibidi's son, who is also a evil wizard, Babadi brings Majin Buu back again to try to take over the universe, with the help of the king of all demons Dubura. Babadi also takes control of vegeta and make him majin, but vegeta let him to become stronger, to try, an defeat his arch rival Goku. Of course after a long struggle and buu blowing up the planet earth the majins were defeated, thanks to Vegetto,(goku and vegeta fused together) They once again use the dragon balls to bring back Planer Earth and everyone killed by majin buu. Later on Goku wishes buu back in the form of ubuu, who is a small tan child with a mohawk like the supreme kais, and with buus orignal power, to be a training parter for goku.