I came to conclusion that it is Madara's "real" body. Or the real Sage of the 6 paths. Why? Because no one can frighten Madara that much. The 4th hokage was strong, yes, but I don't think that would scare Madara off so easily. He might have two bodies for all we know.
Other possible choice:
-Jiraiya (?, doubt it'd scare off Madara)
Other possible choice:
-Jiraiya (?, doubt it'd scare off Madara)

