A battle involving many fighters can be called a battle royal. It is not spelled battle royale unless you are specifically referencing a book, game, or movie by that name. The plural form can be either battle royals or battles royal.
Battles royal were common in England in the 17th and 18th centuries as huge boxing matches. When popularity died out, the practice migrated across the sea to the southern United States. It now exists in the domain of professional wrestling and mixed martial arts.
Twenty WWE superstars took part in a over-the-top-rope battle royal for Bad News Barrett’s vacant Intercontinental title at WWE Battleground. [USA Today]
Estádio Maracanã is readying for Sunday’s battle royal as South American favourites Argentina clashes with European giants Germany, bringing down curtains on one of the most thrilling World Cups ever staged. [Gulf Today]
Elizabeth arguably offers more sheer voice, but Joyce DiDonato musters greater bel canto refinements while both her physical and her vocal acting are extraordinarily proficient; the final result would be a pretty even battle royal had Donizetti not given Mary the bigger opportunities. [Guardian]