A/N: Hello there. This is my prediction of what would happen in chapter 524. Hope you like it!
After waiting for so long after several Shields of Spriggan were defeated, Acnologia finally enters the fray, bored of all the waiting he had to endure. Smelling a dragon slayer nearby, Acnologia turns his attention to Erza and Wendy who prepare to fight him.
"A small dragon slayer? This should be fun." Acnologia begins his attack on the two who barely manage to dodge Acnologia's attack from below which caused a small but powerful explosion near the two. Wendy was quick to enchant Erza's speed to try to outmaneuver Acnologia but his speed surpassed the two easily.
Than, Wendy enchanted Erza's sword with dragon slaying magic and attempted to slash Acnologia across the chest as she did with Eileen but to no avail. Erza was swatted away by Acnologia who turned his attention to Wendy who was absolutely terrified by the amount of magic Acnologia possess.
"An enchanter? Not as strong as that girl I fought earlier…" Acnologia wasn't amused by Wendy's efforts to aid Erza and managed to deal a significant amount of damage to her with a simple wave of his hand. When Erza charged at him with her sword, Acnologia snapped it in two with his hand and bror her arm just as Eileen did.
With that one attack, Erza was sent flying toward Fairy Hills, destroying it completely, which left her completely immobilized. Acnologia slowly made his way toward Wendy who was running low on magic power, unable to fight back due to the sheer amount of magic this dragon possess.
"What should I do? His magic… its massive! Natsu… Erza…help me…" Waving his hand, Acnologia prepared to end the young dragonslayers life here and now. Moment's before he casted an unnamed spell, a blast was sent hurtling towards him and was sent flying away from Wendy after struggling to defend himself from it.
"My my… what do we have here? Are you intent on ending the life of Erza Scarlet? This I simply won't allow." When Wendy turned around, she was shocked to see the enchanter from earlier who tried to kill them both, the strongest female wizard of the 12 Shields of Spriggan. Eileen Belserion.
"Do you intend to get in my way again?" Acnologia asked such a question, to which Eileen happily smiled and began to confront him herself.
Meanwhile, Gildarts was having a difficult time trying to take down August, especially since Cana, his own daughter, entered the fray. She threw more magic cards at August who dodged them with ease and prepared to fire a powerful spell at her but was intercepted by Gildarts who knocked him away with a powerful kick.
"Cana, you need to leave! Now! He's too strong for you!" As soon as Gildarts uttered those words, August casted a powerful spell which left Cana immobilized with Gildarts angrily attacking him who blocked the punch with his staff. This distraction caused Cana to escape the effects of the spell and managed to trap August inside a card.
But thanks to his mastery of countless magics, August escaped with relative ease but jumped away from the two. "His Majesty must defeat Acnologia or we'll all perish for sure."
And now, we shall return to the Fairy Tail guild where Natsu confronts Zeref in the 2nd duel, finally freed of the Demon and Dragon seed deep within him. Natsu charges up a powerful spell and fires it at Zeref who blocks it using his dark magic and throws an orb at Natsu who swiftly dodges the spell without much difficulty.
Using his fire dragon's breath, Natsu is able to deal some damage to Zeref who simply smiles at it as his wounds heal in a matter of seconds. "See, Natsu? You cannot defeat me if you can't kill me. Besides, if I die-"
Natsu was quick to damage him even more with a fire enhanced punch in the stomach, sending him flying away from Natsu. Gray decides to join in by freezing Zeref solid with the use of his Ice Devil Slayer Magic but finds Zeref escapes with ease albeit with minor injuries.
"Ice Devil Slayer Magic huh? Heh." Zeref simply smirks, with Natsu charging at him once more and ends up falling victim to a spell which leaves him completely immobilized. However, Gray merely freezes the spell, allowing Natsu to escape and jumps away.
"Let's do it!" Natsu says to Gray who smiles as the two power up in order to take Zeref down once and for all without killing him.