What I love is the fact Nagato and Itachi haven't even realized he looks almost exactly like Rikudo in that form, I mean Itachi sure, but I thought Nagato might notice.
I guess the only ones who will notice the similarity is Madara and Possibly Kabuto if he has Rikudo's body.
Does Nagato even know how Rikudou Sennin looks like? Hard to believe anyone knows how he looks like, tbh.
I think that when the encounter between Naruto and Nagato + Itachi is about to reach its climax, Madara is going to reach his goal: Kabuto. I think Madara's going to test his 6 Paths of Pain against Kabuto before going to the HQ. Kabuto's already lost a lot of zombies and Yamato's already in the giant flower, anyways. Kabuto will probably then slither away and come to fight another day. The war has gone through so much back and forth without showing any actual interesting action that I feel that if these four do continue fighting, it's gonna be offpaneled.
I think he only knows what Tobi told him, as it looks like only Tobi believed in the legend of Rikudou Sennin until Nagato came along. I actually do wonder whether it's all true or not, as the mutation giving such power does look odd. Reminds me of X-Men, even. :P
It's about two ninja clans, the Iga and the Kouga, who have used selective breeding to develop inhuman abilities and mutations. The heirs to the clans, a young man (Gennosuke) and a young woman (Oboro), each have a special doujutsu. Gennosuke can use his doujutsu to hypnotize an opponent and make them kill themselves. Oboro's automatically negates the abilities of any shinobi who meets her gaze.
There was a fairly recent manga adaptation to the novel called Basilisk (also an anime and a live action movie).