What is this song in Episode 459 of Naruto Shippuden? In Episode 459 what is the background music that plays about 20:00 to last?
The exact version your asking about was an unreleased OST, but it is known as Kaguyas theme. The full song begins ~18min mark on episode 459 and you can listen to it here

Credits to a user on this Naruto discussion board for finding it