User blog comment:B214/Question and Answers 2/@comment-24378967-20140122142943/@comment-1359322-20140122143509

Volume 17 isn't released yet nor have we seen any hints of what might be Rossweisse's hidden ability so truth be told, it's all speculations right now. Also there's no bombardment magic, Ross just releases all her Norse magic in battle, so it's more accurate to say magic bombardment.

But i think the magic bombardment isn't something limited to Ross, maybe any Valkyrie with proper training could do that too.