Complex sentence: The remaining members of the League of the Scroll have also descended upon the Stone in hopes of unraveling an ancient prophecy that if deciphered could reveal to Josua and his army the only means of striking down the unslayable Storm King.
Split into simpler sentences: The remaining members of the League of the Scroll have also gathered at the Stone in hopes of unraveling an ancient prophecy. If deciphered, it could reveal to Josua and his army the only means of striking down the unslayable Storm King.