So I haven't figured it out yet, but with al that is said in chapter 1037 it could be possible that Zunisha ate the devilfruit they are talking about and he is the lurking legend Oda told about. The Gorosei said the devilfruit is a legend and hasn't awakened for centuries. That is because Zunisha has been alive and hidden all this time. For now this is all I want to share. Maybe you all can help and I can edit the theory in the future.