Gnork was an Ogron.
Dr Linus Leofrix captured and mentally augmented him as part of an experiment to create super soldiers to conquer the galaxy. However, the augmentations led to Gnork becoming even smarter than Leofrix and escaping his control. He took Leofrix's spacecraft and left the Ogron planet, stranding Leofrix and his pilot Rostow, who were presumably killed by the other Ogrons. (COMIC: Warlord of the Ogrons)