Board Thread:Wiki Discussions/@comment-25217769-20140723231559/@comment-1512913-20140801123431

How do you know that? We don't know when their to-death battle took place, but in my opinion after Hagoromo's death (thus with Tailed Beast existent already) because I don't think Hagoromo would just sit and watch them kill each other.

And we know nothing of Ashura's personality other than he gained power through hardship and friendship and spread Ninshu which didn't work. He might have turned insane later on.