Brain

Brain, or Zero (ゼロ Zero), is the leader of the the Oración Seis guild, a dark guild composed of highly powerful Mages whose goal is to find a very destructive power known as Nirvana that was sealed away long ago.

Appearance
Brain has neat silver hair that reaches his shoulders with dark skin. He has markings on his face that take the shape of straight black lines that disappear when the members of the Oracion Seis become incapacitated or killed. He is slightly taller and more muscular than average. After Brain's alter-personality Zero is unlocked, his appearance changes slightly. His hair becomes more wavy and his skin turns to a more pale color.

His Oracion Seis mark is on his chest.

Personality
He does not respect his opponents, as he often calls them trash or maggots. He is willing to do all that is needed to achieve his goal, Nirvana. As a leader of a dark guild, he is cruel even to his comrades, as he attacks Cobra for losing to a regular guild. His comrades are just puppets for him, as he says, he can just find new ones, when Nirvana is activated. He has two personalities: There is the face he shows to the world, which loves fame and goes by the codename of "Brain" and another hidden face, which loves destruction and goes by the name of "Zero". Brain may be disrespectful and cruel to foes and allies alike but Zero just seeks to destroy everyone and everything. Zero states that out of his perspective if someone or something has still some kind of form, he, she or it is worth destroying. This kind of thinking even made him kill the seventh member of Oracion Seis, Klodoa, without the latter provoking him in any matter. Brain seems to be somewhat afraid of his other self, Zero, so as a consequence he used every Oracion Seis member as a "key" to lock his other personality away and when he was defeated, even warned the Light Alliance about him.

History
Brain once worked in a Magic development department where he created hundreds of types of Magic, one of those being self-destruction Magic that he taught to Jellal.

Brain was also responsible in taking five children with the highest Magical power at the time from the Tower of Heaven and trained them to become members of Oración Seis Guild, and six key, which sealed his other personality, Zero, who only loves destruction.

Oración Seis arc
In the battle with the alliance consisting of Fairy Tail, Blue Pegasus, Lamia Scale and Cait Shelter. He doesn't take part, allowing the others to deal with them. Once their opponents have been defeated he goes to finish it with a spell called Dark Rondo, gathering a mass of dark energy above him through his staff. Before he can fire it though, he spots Wendy Marvell and suddenly hesitates. Implying that, like Natsu Dragneel, he has seen her before.

After he gets over his shock, Brain proceeds to kidnap her (and Happy unintentionally since Wendy grabbed him as she was being taken) and depart the battlefield, firing the intended spell at the other defeated members to finish them off. Though unknown to him, Jura Nekis had saved the alliance at the last second. Brain then takes Wendy and Happy back to the Oración Seis's base and informs the other Oración Seis members of Wendy's healing Magic. He then has Racer bring in a coffin while the others continue to look for Nirvana. After Racer does so, he opens it and reveals Jellal inside. Brain then explains to Wendy that he wishes for her to revive him since he could easily lead the way to Nirvana (as Jellal was in the Magic Council and thus knows it location from them) and that Wendy, who oddly enough knows Jellal, owes a debt to him as well. When Wendy hesitates, Brain grants her five minutes to make her decision. Ultimately she chooses to revive Jellal much to Brain's delight. However no sooner then Jellal recovered, he turns on Brain and knocks him to the lower levels of the hideout before leaving. Angered at this and believing Jellal trying to take Nirvana for himself, he has Cobra track down Jellal hoping he'll lead the Oración Seis to what they seek.

After Racer kills himself (or attempts to kill himself in the anime), an angry Brain awakens Midnight to kill the Light Team. As he continues to look for Nirvana, he sense that Angel has died as well and vows to not let their sacrifices go in vain (however, Angel is still alive). He finally arrives at Nirvana where Cobra tells him in a panicked state that Jellal has placed a self-destruction Magic on Nirvana. He is not worried, revealing that he has an extensive knowledge of Magic and easily cancels the self-destruction. Proclaiming Nirvana now his he activates its second stage, and Nirvana shows it true form. He states that the legal guilds' strongest weapons, "trust and unity", are now useless. Natsu later manages to reach the control center to which Brain sends Cobra to defeat him. However Natsu manages to beat Cobra and knocks him back into Nirvana after a midair battle.

Cobra manages to get back to his feet despite his wounds and goes to finish the now weakened Natsu off but Brain attacks Cobra from behind, mortally wounding him. Surprised by this betrayal, Cobra listens to Brain's hearts and see that he thinks the Oración Seis weak for being defeated by a "common guild' before collapsing. Natsu questions why Brain would attack his own comrade which Brain answers that he has Nirvana so he can create a new Oración Seis. He plans to start with Natsu after witnessing his power against Cobra. However as he drags Natsu to the control center, he runs into Lucy Heartfilia, Gray Fullbuster and later Jura. The power going to his head, Brain comments on how no one can stop him and his plans to start with Cait Shelter. Jura attacks him instantly, knocking him into a few stone structures before proclaiming he won't let Brain rest until he reveals his reasons for attacking that specific guild. Brain is easily defeated by Jura, but is still conscious and still has a way to get rid of the them. Natsu and the rest of them realize that even though they have defeated Brain, Nirvana is still heading towards Cait Shelter. Brain then pretends to be Hoteye and sends a message to the group, saying that Midnight is in the room below the King's Room and that if he is defeated then Nirvana will be stopped. But unbeknownst to them, Midnight has actually encountered Jellal and Erza, and that the room under the King's Room is actually a trap set up by Brain. However they were too late to realize this and were caught up in a huge explosion when they reached there.

When Midnight is defeated by Erza, it is revealed by Klodoa that all the Oración Seis members were acting as keys through living link magic to keep "another" personality within Brain sealed. However, now that they have all been defeated and thus all the keys unlocked, this new personality that loves to destroy has awakened. This new personality is codenamed Zero and differs to the normal Brain by having black dilated eyes and white skin. When he arrives at Natsu, Gray, Lucy and Happy's location he quickly defeats all of them and sadistically keeps attacking them even though they have been downed. Just then, Nirvana finally arrives at Cait Shelter. Klodoa states that the destruction of the guild will make sure Nirvana can not be resealed; however, Zero shouts that such a reason is meaningless: he needs no reason to destroy. He then orders Nirvana to fire. However the shot is diverted due to the Blue Pegasus ship hitting one of the leg and knocking it off course. A revived Hibiki as well as the other Trimen members and Lyon and Sherry are show piloting it and keeping it in the air. Hibiki informs the others of Niravna's weak points through his archive Magic. But Zero intercepts the message, taunting the group that he knows where the weak points are and won't let them destroy it.

Unknown to him however, the other manage to get through to the fallen Fairy Tail members and encourage them to get them back to their feet. They get up and say that of course they can get up. Everyone picked a number between one to six for the Lachryma crystals and Natsu chose number one right away. Which leads him straight to Zero, because of his keen sense of smell he knew that Zero was there. Zero asked him what business he had left and Natsu replied by saying who's going to be destroyed in the end. The two start to duke it out again in which Zero explains that his powers are not exactly the same as Brain, but not before commenting on Natsu's performance being better than the previous battle despite being heavily wounded. He fired a Dark Capriccio from his hand and controlled it to continually attack Natsu. However Natsu managed to block it head on which impressed Zero, but the battle was interrupted when Natsu got shot at by Jellal.

Zero then states that Jellal's memories must have returned. However, he noticed that something was odd when Jellal told Natsu that he knew fire-based Magic wouldn't hurt him. Zero came to realize that Jellal did not regain his memories in which he replies that he remembers Natsu's name. A name which brings hope. While Natsu threatens Jellal, Zero says that they should fight somewhere else since they are annoying him. He then proceeds to attack them both with a Dark Capriccio to which Jellal blocks with his body to protect Natsu. Natsu then accepts the Flame of Rebuke from Jellal. Zero then states that by taking it he also shares his sins. He replies back by saying that Fairy Tail is no stranger to sins, and that the real sins are to ignore and stop believing in others. The two duke it out again but this time Natsu gains the upper hand. For the first time Zero seems frightened when saying "Dragon Force". Zero remembers that power being similar to the Dragons - a power can destroy everything. The word destroy rekindled his interest to continue fighting him. However, it is Zero this time that is gaining the advantage and attempts to blast him out through the ground. Continuing to press his attacks on Natsu he than states that he hasn't learn to fully use it yet. Disappointed, he mentions that the Dragons' power once ruled the ancient world and questions that power he is facing is the same level as back then. He says to Natsu that he can't handle him on his own. Natsu answers back by saying that they are all supporting him and the power is flowing through him. Zero had enough and is pitied that he will have to kill Natsu, but he did enjoy the battle and gives him his best naught by his utmost Magic. Zero and Natsu both of then fight it all out with their strongest attacks: Genesis Zero and Guren Bakuenjin respectively.

Zero hits Natsu full force with the attack and for a moment it looks like it'll overwhelm Natsu. However, Natsu manages to plow through, completely burning through and nullifying Zero's Magic. Then Zero realizes in horror that Natsu Magic is that of a Dragon Slayer before he is hit by Natsu's Guren Houou Ken (Lotus Phoenix Blade) and tackled into the Nirvana core he was guarding. Smashing and destroying it (as well as knocking Zero completely unconscious) just as the members of the Light Team do the same to the other Nirvana cores, stopping the device once and for all. With this victory, Zero was completely and utterly defeated.

Magic and Abilities
Caster Magic User: He seems to be quite intelligent and has an extensive knowledge of Magic, having created hundreds of spells in the past and knowing how to easily undo self-destruction Magic cast by Jellal even without the cancellation code. His general knowledge seems to be large as well given how he recognises Wendy as a user of lost Healing Magic and her past with Jellal. He kidnapped Wendy with his primary Magic Darkness Magic for that reason. As stated by Zero, Brain possesses the same magic as Hibiki Laytis. This could explain how he has such a vast knowledge of Magic and how he may have known about Nirvana and Wendy. It also appears to be an extremely rare ability as Zero thought that this spell was unique to Brain. One of the many spells Brain invented is Self-Destruction Spell, and he is familiar enough with it to dispel them when casted by Jellal without knowledge of its cancellation code. He also can use Requip Magic to change his clothes. As Zero his Magical abilities and even physical features are increased intensively. Zero can use all the same Magic as Brain, but has much greater control over them and their strength increases to an great extend.

Enhanced Strength (as Zero): He seems to be quite strong, because he managed to pummel Natsu, who, through his Dragon Slayer magic, is an expert in close range fighting, with nothing more but his sheer fists.

Enhanced Durability (as Zero): In his fight against Natsu in his Dragon Force form, he has shown an enhanced degree of assimilating enormous amount of damage without much problems. Just the full release of Natsu´s magical power could damage him seriously.

Enhanced Magical Power (as Zero): Zero has immense magical power. He can release his magical energy into a potent aura around him, which can even make the ground shake around him. The Light Team described his magic as the most disgusting magic they have ever felt.

Darkness Spells
 * Dark Capriccio (常闇奇想曲 Tokiyami Kisōkyoku lit. Capriccio of Eternal Darkness): A beam of darkness is fired from his staff (or in Zero's case, his hands), meant to be used as a drilling offensive attack that can pierce through defenses. Zero, however, has far greater control and is able to manipulate its movement with one hand, cast more than one beam at a time and even use it as a whip. "Capriccio" refers to a music style which is free in form.
 * Scream: A stronger and faster version of the technique. (Anime only).
 * Zero Slash: Zero uses Dark Capriccio as a whip and attacks the enemy. In the manga, this attack is unnamed.
 * Dark Gravity (ダークグラビティ Dākugurabiti): As its name implies, it amplifies the gravity in a certain area. When used against Natsu, he was sent crashing downwards through Nirvana's lower floors.
 * Dark Rondo (常闇回旋曲 Tokoyami Kaisenkyoku lit. Rondo of Eternal Darkness): When casted, dark Magic with horror-stricken faces swirl around Brain's staff (or Zero's hands), becoming more and more condensed. Brain can then fire the gathered Magic on a wide scale (as he did against the Light Alliance) or focused at an enemy. However, this spell was stopped by Jura Nekis's Iron Rock Magic. "Rondo" is a music form derived from Italian which is based on recurring elements.
 * Dark Delete: Several spheres of darkness are fired continuously from Zero's hands. In the manga, this attack is unnamed.
 * Genesis Zero (ジェネシス・ゼロ Jeneshisu Zero): Zero's strongest Magic attack. He first charges green darkness energy on his fingers and summons thousands of black phantoms to strike at his foes to the point of them being engulfed completely by their sheer numbers alone. This technique has been claimed to be capable of erasing a person's soul and their very existence.