Majin Piccolo is the majin version of Piccolo. He tried to defeat Omega Shenron in this state in Hell but failed. After the events of GT, Omega was sent to Hell. He killed everyone to keep his body. After this he was in Hell killing everyone and Piccolo was there to stop him. He consulted Babidi to do the same thing that he did to Vegeta. Babidi did as told and turned him into a majin.