Board Thread:Theories & Speculation/@comment-1512913-20141028151348/@comment-945885-20141031203019

That seems unlikely. They were a clan of otherworldly travelers searching for the Divine Tree, and only arrived about one millennia ago. Kaguya was already their leader at the time, and she ruled as a tyrant.

Most likely, Hagoromo used the sword to fight the Ten Tails, reshaping some of the landscape in the process.