We can see that shit is going to get serious here, every spriggran seems to want revenge except for brandish who is sort of upset. From now onwards it might be difficult for the fairies to fight because their tactician, Mavis, can't think thanks to that collar she has. As for Natsu, Lucy, Juvia, Gray and Erza they seem to have high hopes and during the battle they will surely recieve reinforcements. The fight against the 'common soldiers' shall be easy since Natsu and Company have gain more strength from training when Fairy Tail disbanded, Natsu and Erza will surely take out most of the soldiers. Lucy might reveal a new stardress, I'm hoping for Scorpio form or Capricorn form, or maybe once again Aries form because we didn't see its powers. As for the historias, I think it will be easier than defeating the spriggan twelve who are alive.
Here is one of my theories; If Eileen takes out Fairy Heart from Mavis, Mavis might die causing [maybe] some sort of big reaction on Zeref.
And that Natsu and Zeref will have a small encounter in chapter 495 but a spriggan will interupt in form to protect Zeref