Irene Belserion vs. Acnologia

Irene Belserion vs. Acnologia is a fight fought between the Spriggan 12 Irene Belserion and the Dragon King Acnologia.

Prologue
The mighty forces of Alvarez Empire finally make their move on Ishgar and attack from all directions, with the east side being pressed on by God Serena as Four Gods of Isghar struggle against him. Facing imminent defeat, Warrod begs for someone to stop this powerful foe from reaching Fairy Tail and that is when they are approached by immense magic power: Acnologia arrives, in his search for Dragon Slayers, and strikes down God Serena, beginning the countdown of Dragons' true demise.

Meanwhile, a new danger makes its appearance in the north, as revealed by Brandish to the rest of Fairy Tail, the one who shares the title of the strongest with August: Irene Belserion, dubbed as "The Crimson Despair". At Zonia, the sacred mountain in the north, Irene reminisces about the tale of two angels clashing there, indulging in a discussion about it with her two subordinates. Afterwards, she proceeds enchanting all of the mountain, changing its cold temperature into that of spring and orders Larcade and Bloodman to give a "warm welcome" to the arriving forces of Fairy Tail. However, Irene soon senses that there are two more parties on the way, dubbing the last one as the most troublesome, requiring her full attention.

Being completely serious about the matter, Irene raises her staff and begins enchanting her surroundings. She comments the war will have to be brought to a swift end, as the troublesome one appearing is no one but Acnologia. In spite of that, Irene is completely confident in her plan, intending to come out victorious. Meanwhile, Acnologia makes his way towards the mountain. Sensing Gajeel's struggle for life and his subsequent disappearance, Acnologia pronounces his plan to destroy all the Dragons nearing its completion, which is noticed by Irene, who approaches the Dragon King. Having no interest in Irene, Acnologia simply tells her to go away, however, as he realizes that she is fully aware of his identity, Acnologia wonders if Irene can amuse him in any way, getting a positive answer from the woman.

Battle
Beginning the entertainment, Irene releases her magical power through her staff and Acnologia's confident look is changed to that of a surprise as a huge mass of flames suddenly bears at him from the side. He defends himself with his right arm, however, the force of the spell is so strong that the ground below his feet begins to be crushed. Acnologia then recognizes the spell to be an atmospheric enchantment, however, Irene is not done as she uses her staff to point it at her target. The ground below Acnologia is destroyed even further as Acnologia faces a sudden force that throws him away, smashing through nearby surroundings until he is able to stop himself and get back on his feet. Acnologia smirks as he describes Irene's ability to be that of a High Enchanter and then laughs even more as he raises his arm, causing the ground below Irene to explode. Irene dodges with a tumble midair and lands on her feet, relieved that she has managed to do so. The two exchange compliments, as Irene notices that the hole caused by Acnologia's Magic is so deep that its bottom can't even be seen. She then plays with the idea of Zeref claiming Fairy Heart, pointing out the possibility of even Acnologia falling to the Black Mage in such case.

Acnologia realizes the purpose behind Irene's words and states that he has no intention of waiting, with Irine acknowledging that she indeed cannot afford for Acnologia to get in their way. She points out that Zeref is thinking of this as nothing but a game, so she will be the one to bring this war to its conclusion. As Irene says that, she hits the ground with her staff, causing an enormous amount of light to erupt. Acnologia watches this with a surprised expression, realizing that not even he recognizes this Magic. Dubbing it as "Magic of the New Era", Irene explains that this is indeed something that no one would know of even 400 years ago. Further observing his surroundings, Acnologia realizes that Irene is enchanting all of Earthland, with Irene specifying it to be only the land of Fiore. Curious about her identity, Acnologia poses the question and the woman simply states that she is called "Irene", wishing that she and Acnologia can meet once more. The Magic, Universe One is then activated and all of Fiore is covered in bright light.

Aftermath
Below the Fairy Tail's guild building, Mavis finally wakes up after having her real body freed by Cana. Unable to find anyone nearby, Mavis walks to the guild hall just to happen upon Zeref himself, a direct result of Irene's Magic, as Zeref reveals to Mavis. Meanwhile, all other members of Fairy Tail wake up at random locations, realizing the changes to their surroundings. Irene's intention is revealed to be having Zeref put as close to Fairy Tail as possible, while making sure that Acnologia is sent away. Irene himself acknowledges the results of the Magic being used for the first time as quite favorable, even though she has no knowledge of her own location: finding herself in the throne room of Mercurius, facing the shocked members of the royal family.