The facts are somewhat murky. There were accounts in old records of a person named Edward Mordrake who had a strange deformity. It was said that he had a face on the back of his head. However, it's difficult to determine how much of this was based on real medical conditions and how much was superstition or misinformation of the time. Some believe that it could have been a very rare congenital defect that was misinterpreted in the context of the era's limited medical knowledge.
Well, the main fact that has been passed down is the existence of Edward Mordrake himself with his extraordinary condition. There are reports that he was a real person who suffered from what was seen as a very abnormal and disturbing physical feature. However, in the absence of modern medical examinations and proper documentation from that time, it's hard to be certain about all the details. It's possible that his condition was a result of a genetic mutation or a very rare medical disorder. Also, the social and cultural context of the time might have influenced how his story was told and perceived, adding elements of mystery and horror that may or may not have been entirely accurate.