Acnologia

Acnologia (アクノロギア Akunorogia), also known as The Black Dragon (黒龍, Kokuryū), and fearsomely reputed as The Black Dragon in the Book of Apocalypse, is a powerful Dragon that assaulted the Fairy Tail Mages on Tenrou Island in the year of X784.

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. His lower body, specifically his belly, inner tail and legs, is grey in color, and seems to be rather smooth. He possesses a blunt, rounded head with four large and elongated plates extending backwards, and has white beady eyes. His 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 his whole body, which take on a formation reminiscent of a bird’s feathers. His massive tail splits in two at its end, where the black plates disappear, and takes on a double stinger-like appearance.

His appearance before becoming a dragon was that of a human, who, after defeating many dragons, his skin became scales, his teeth became fangs and his entire form changed to that of a dragon.

Personality
While some other Dragons appear somewhat friendly to Humans, Acnologia is antagonistic towards them, and views them as insignificant, even though he once was one of them. As Zeref puts it, it sees them as nothing more than insects pestering him, which is why he does not even respond to them, when they try to converse with him.

History
Born as a human over 400 years ago, Acnologia became one of the first Dragon Slayers who entered the Dragon Civil War. However, ignoring both sides of the conflict, Acnologia started killing countless dragons from both sides. As he continued to bathe in the blood of dragons, and, thought to be done with the aid of Zeref, Acnologia's physique eventually turned to that of a dragon, proclaiming himself to be the Dragon King. This event was to be forever known as the Festival of the Dragon King.

For many years, Acnologia has roamed Earth Land and was renowned as an infamous, feared Dragon, that was known for single-handedly wiping out an entire country. At some point in time, Acnologia ran into Gildarts Clive when the Mage was on his "100 year quest" on Zonia Mountain. In an instant battle, 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, thus leaving him the first human to see Acnologia and live to tell the tale.

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 in his Titan mode. As the two fight, Acnologia is eventually able to knock Makarov to the ground. Just as he 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 of 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.

Magic & 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 is fired in the form of a giant beam it is capable of causing a huge explosion, which was enough to create a gigantic crater in the water surrounding Tenrou Island and Cana Alberona even believed that it would be able to destroy the island completely.

Flight: Being a dragon, Acnologia possesses the ability to fly, using its large wings to travel over long distances, maneuver 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 Strauss who was utilizing her Satan Soul form and the ones from three different Dragon Slayers, whose Magic is supposed and thought to be able to slay Dragons, were utterly useless against it.

Immense Strength: Given its gargantuan size, Acnologia is capable of easily reducing a wide area to rubble simply by landing on it after flying high up into the sky, and engage head-on 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.

Former Magic & Abilities
Dragon Slayer Magic (滅竜魔法 Metsuryū Mahō): Acnologia was one of the first Dragon Slayers created to fight in the Dragon Civil War. However, he and the other Dragon Slayers turned on them and slayed them as well. Acnologia killed many dragons until he, with the help of Zeref, was turned into a dragon.

It is currently unknown which type of Dragon Slayer element he formerly used.

Battles & Events

 * Fairy Tail vs. Acnologia
 * Dragon Civil War