Board Thread:Theories and Speculation/@comment-25576506-20150406220206/@comment-5936871-20150408042958

I believe the "power" Hagoromo left behind for Asura was simply Asura being Hagoromo's successor of Ninshu and Indra was jealous because he wasn't chosen. That is what sparked him to engage in a feud with Asura that would last for centuries through their descendants the Senju and Uchiha. Asura's chakra mode is something unique to him that was never explained and maybe the anime will go more in-depth about it.