Acnologia

"Fear? As if I would be like one of the demons of Zeref's books? Don't make me laugh! I am the king of dragons, Acnologia!"

- Acnologia to Igneel

Acnologia (アクノロギア Akunorogia), also known and fearsomely reputed as "The Black Dragon" in the Book of Apocalypse, is a puissant Dragon and an enemy of humanity. He is one of the main antagonists of Fairy Tail.

Appearance
Acnologia is a mastodonic dragon whose entire upper body, is covered in black, round scales, which in turn are decorated by spiraling, blue markings. Its lower body, specifically its belly, inner tail and legs, is grey in color, and seems to be rather smooth. It possesses a blunt, rounded head with four large and elongated plates extending backwards, and has white beady eyes. Its mouth is full of sharp teeth, and below it is an elongated protrusion pointing downwards. Acnologia’s gargantuan, multi-layered wings are composed of the very same plates covering its whole body, which take on a formation reminiscent of a bird’s feathers. Its massive tail splits in two at its end, where the black plates disappear, and takes on a double stinger-like appearance.

Personality
While other Dragons appear somewhat amicable to humans, Acnologia is inimical towards them, and perspectively scrutinizes them as infinitesimal. Zeref words it, "it sees them as nothing more than insects pestering him".

History
Prior to the beginning of the series, he was born as a human over 400 years ago. He was originally one of the first Dragon Slayers during the Dragon Civil War to support the coexistence of both humans and dragons. Unfortunately, Acnologia and other Dragon Slayers turned against their own dragons, killed them, and bathe in their blood. Originally believed to be done from the aid of Zeref, Acnologia physically turns into a dragon, and proclaimed himself to be the Dragon King. This event was forever etched into history as the Festival of the Dragon King.

For many years, Acnologia was feared by the people of Earth Land, as he was credited with the single-handed destruction of an entire country. At some point of time, Acnologia ran into Gildarts Clive when the Mage was on his "100 year quest" on Zonia Mountain. In an instant, Acnologia took Gildarts' left arm, left leg, and an unspecified organ, leaving him to die before flying away, though Gildarts managed to survive, albeit with difficulty.

Tenrou Island Arc
Acnologia comes to Tenrou Island, wreaks havoc on it, and fights the Fairy Tail members on the island. In the battle, it causes so much devastation that Makarov is forced to hold him off to allow the other Fairy Tail Mages to escape. As the two fight, Acnologia is eventually able to knock Makarov to the ground. Just as it is about to kill Makarov, all of Fairy Tail comes back and starts attacking the dragon. Acnologia then flies into the air, and seemingly destroys Tenrou Island, and all the Fairy Tail members on it with his Dragon's Roar.

After these events, Acnologia takes back up to the skies and disappears from sight.

Tartarus arc
Acnologia appears one more time at the ruins of Cube where the battle between Fairy Tail Mages and Tartarus takes place. As he nears his destination, both Mages and the Demons take notice of his presence.

Acnologia appears one more time at the ruins of Cube where the battle between Fairy Tail Mages and Tartarus takes place. As he nears his destination, both Mages and the Demons take notice of his presence. Effortlessly, Acnologia creates huge explosions with his breath, as well as shockwaves with his wings alone, much to the Mages' despair. He approaches Mard Geer and the Demon deduces that the Black Dragon is after E.N.D. However, Acnologia's rampage is temporarily interrupted, as Igneel, released from within Natsu's body, attacks him, with an intention to stop his rampage. Acnologia and Igneel begin to clash, while all the Mages below watch in horror and awe. After Natsu jumps on Igneel, the latter fires a huge flame blast towards Acnologia, although the beast easily shrugs off the attack and comes out of it unscathed. Acnologia is then later punched by Igneels' version of Fire Dragon's Iron Fist, however he shrugs this attack off as well.

Shortly thereafter, taking advantage of Igneel's worry for Natsu, Acnologia fires a Dragon's Roar at his opponent's head, but misses. Acknowledging Igneel as his enemy, Acnologia speaks to him, citing his displeasure at the existence of Dragons; he ends his comment by saying that he will slay Igneel. As the fight goes on, Acnologia tells Igneel that he won't escape. However, the latter explains that he didn't intend to run, and that he moved so that he can fight without holding back, in order to defeat the other creature. Acnologia, however, says that it won't be a simple defeat, but an one-sided obliteration. Later as the Face bombs across the continent begin to detonate, Acnologia is sent plummeting towards the earth extremely wounded, much to everyone's surprise. His body is then used as a victory stand by Igneel, who announces the arrival of the other Dragon Slayers' foster parents to stop the mighty threat of the Magic Pulse Bomb.

Acnologia doesn't stay down for long though, as he slashes out at Igneel and takes their battle back up into the sky. There, he questions Igneel's motives for having the other Dragons hide inside their foster Dragon Slayer children, and, when Igneel asks if he is scared of E.N.D. reviving, berates the Fire Dragon and declares that all he wants is utter destruction. Acnologia quickly overwhelms Igneel and repeatedly crushes his torso with his claws whilst screaming about destruction; he also derides the Dragon for being the Flame Dragon King yet not being able to fight equally with him and continues his relentless assault. Acnologia is then quickly overtaken by Igneel and loses his left arm, however in return,

Acnologia destroys nearly the entire left half of Igneel's torso and then kills him with his Dragon's Roar.

Powers and Abilities
Dragon Roar: As all dragons and Dragon Slayers, Acnologia can perform a breath attack of its element. It is unknown what such element is, but once it's fired in the form of a giant beam it is capable of causing a huge explosion, which was enough create a gigantic crater in the water.

Flight: Being a dragon, Acnologia possesses the ability to fly, using its large wings to travel over long distances, manoeuvre high up in the air and perform aerial assaults on those below it.

Immense Durability: Acnologia was shown capable of shrugging off all the attacks from the Fairy Tail members who came to Makarov's aid. Even those from Mirajane in her Satan Soul form and the ones from three different Dragon Slayers, whose Magic is supposed and thought to be able to harm dragons, were utterly useless against it.

Immense Strength: Given its gargantuan size, Acnologia is capable of easily reducing a wide area into rubbles simply by landing on it after flying high up into the sky, and to engage in a physical confrontation with Makarov in his Titan form, injuring him in the process and eventually gaining the upper hand. Despite easily dominating the various Fairy Tail members, many of which possessing S-Class abilities, on Tenrou Island, Gildarts claimed that Acnologia was not using the same level of power it did back during their past confrontation, and that it seemed like it was just playing around with them.

Major Battles

 * Fairy Tail vs. Acnologia
 * Igneel vs. Acnologia