Natsu Dragneel & Happy vs. Cobra & Cubellios

Natsu Dragneel &amp; Happy vs. Cobra &amp; Cuberos is a fight fought between Mages of Fairy Tail, Natsu Dragneel and Happy, and Dark Mage of Oración Seis, Cobra, and his pet snake, Cuberos.

Prologue
In order to destroy Nirvana and free Erza from hatred and sadness, Jellal casts a Self-Destruction Spell spell on it and himself, planning to die with the cancellation code. However, Brain is able to undo it, being the one who taught the spell to Jellal in the first place. Erza tries to attack Brain but he already ordered Nirvana to awake, causing the ground to crumble. Nirvana is then revealed to be a giant city with six legs.

In order to stop Brain, Natsu, Gray and Lucy climb one of Nirvana's legs. When Nirvana begins to move, Natsu's motion sickness kicks in, causing him to fall off the leg. Suddenly, Happy, using Aera, arrives and grabs hold of Natsu and the two heads towards Nirvana. The two fly over Nirvana and notices that it looks like an Ancient City. Natsu then picks up the scent of Cobra and the two head for the King's Area. Once there, Natsu immediately attacks the ground which cancels Brain's Magic Circle. Natsu then uses a Fire Dragon's Roar on Brain who shields himself and orders Cobra to get rid of Natsu.

Battle
Cuberos, under Cobra's orders, attacks Natsu and Happy sending them a short distance away from Brain. Natsu tries to counter with another Roar but Cobra, jumping off Cuberos, attacks him. After recovering from the attack, Natsu and Happy are surprised to see that Cuberos is able to sprout wings of its own. Natsu and Happy conclude that Brain is the one controlling Nirvana and try to use a feint attack. However, Cobra is able to see through is and attacks Natsu with Cuberos' tail. After multiple failed attempts to attack Brain, Natsu and Happy begin to wonder what kind of Magic Cobra uses. Cobra merely smiles at them and thinks that he is going to enjoy their fight.

As the battle continues, Natsu and Happy notice that Brain managed to restore the Magic Circle on top of the King's Area. Natsu and Happy are unable to stop him due to Cobra's interference but Happy is confident that they will be able to beat Cobra with their teamwork. When Brain tells him to finish the two, Cobra orders Cuberos to attack but Natsu and Happy are able to dodge. Natsu then counters with his Fire Dragon's Iron Fist but misses and is attacked by Cuberos' tail. Natsu tries to attack again by sending multiple Fire Dragon's Iron Fist but Cobra and Cuberos easily dodge his attacks. Natsu becomes exhausted due to using too much Magical Energy and Cuberos attacks him with its tail again, sending him flying across the sky. Cobra reminds him that he can hear his thoughts but Natsu and Happy ignore him and charge at him. However, Cuberos sends the duo to the ground.

Happy is able to stop them from crashing and begins to fly to the sky again. However, Cobra and Cuberos suddenly appear and attack the two. The duo dodges the attack and Happy flies into one of the buildings. Natsu devises a plan to attack Cobra by hiding in the corner. The wall begins to crack and Natsu moves in front of it, ready to attack. However, Cobra attacks him from the side and reminds him that he can hear him.

Natsu tries to attack Cobra again but misses. Happy concludes that Cobra possesses a kind of mind reading magic but Cobra tells him that he uses Listening Magic that allows him to hear their thoughts. Happy decides to try him, clearing his mind of nothing but fish. He ends up surprised when Cobra manages to hear him. Natsu tests him too by thinking of a joke and Cobra ends up laughing. Natsu and Happy realize the difficulty of their situation and Happy tries to devise a plan. However, Cobra hears his plan and voices it out loud. Cobra then continues to read all of Natsu’s plans much to Natsu’s dismay. Angered, Natsu and Happy charge at Cobra and attacks him with a barrage of punches and kicks. One of Natsu’s attacks manages to graze Cobra, much to Cobra’s surprise. Natsu uses this as an opening and continues to attack Cobra. Cobra is surprised when he hears nothing coming from Natsu’s head, realizing that he is attacking without thinking. Cobra then grabs one of Natsu’s hands and burns it with poison, revealing that he is the Poison Dragon Slayer.

When Natsu and Happy express their surprise about his revelation, Cobra immediately attacks them with claws. Natsu and Happy narrowly dodge the attack and realizes the difficulty of their battle. Cobra then jumps off Cuberos and, with his feet coated with poison, kicks Natsu. Cobra's attack burns Natsu's skin and Cobra reveals that his strikes are able to decay anything that it touches. Natsu ignores this and charges at Cobra with his Fire Dragon's Claws. Cobra defends himself by using his Poison Dragon's Fang Thrust. The two attacks cause an explosion and Natsu and Happy begins to precipitate. Happy uses his Aera and grabs Natsu. The two then charge at Cobra but Cobra manages to dodge all their attacks. Seeing their disadvantage, Natsu and Happy begin to argue about Natsu attacking without thinking. While watching his opponents, Cobra looks at Cuberos with a disappointed smile. Natsu and Happy then charges once more. Natsu uses his Fire Dragon's Claw while Cobra uses his Poison Dragon's Spiral Jaw. Natsu and Happy are overpowered and falls to the ground. Natsu and Happy's fall cause a ball of fire to fall on top of them, causing an explosion. Cobra searches for his opponents from the sky when he hears a strange sound. The sound is revealed to be coming from Natsu who is eating the fire from the explosion to replenish his strength.

With his strength replenished, Natsu begins to charge at Cobra. Annoyed, Cobra attacks with his Poison Dragon's Scales but misses when Happy uses his Max Speed. Natsu and Happy tries to stage a feint attack but Cobra is able to see through it and stop Natsu from attacking him. Natsu tries to attack with a close-range Fire Dragon's Roar but fails when Cobra grabs his mouth and throws him aside. Happy is able to save Natsu from falling when Cobra reveals his ability to eat Cuberos' Poison Mist. Cobra then attacks with his Poison Dragon's Roar which hits Natsu and Happy. Natsu and Happy begin to lose altitude due to the effects of Cobra's attack. Cobra reveals that his Roar infects the target's body with poison that slowly kills them from the inside. Believing that he already won, Cobra is surprised to see that Natsu and Happy are still determined to fight. Natsu attacks with his Fire Dragon's Wing Slash but Cobra is able to dodge since he is able to hear Natsu's movements. Cobra is impressed that Natsu is able to last long when he is infected with his poison and addresses him as an Old-Style Dragon Slayer. Cobra reveals that he is a New Generation Dragon Slayer, with Dragon Lacrima infused in his body. Natsu and Happy realize that Cobra is similar to Laxus and conclude that he is not a real Dragon Slayer since he did not learn it from Dragons. Cobra disagrees, telling Natsu that Dragons do not exist. Enraged, Natsu charges at him but misses. Cobra continues to say that Dragons are extinct and attacks Natsu with his Poison Dragon's Twin Fangs. Natsu and Happy begin to feel the effect of the poison and are unable to move their bodies. Natsu tells Happy to drop him on top of Cobra. Happy tries to protest but Natsu forces him to agree, planning to finish the battle with one move. Cobra is able to hear that Natsu is planning to use a Full Power Dragon Roar and readies himself to end the fight himself. Happy lets go of Natsu who begins to fall on Cobra. Cobra jumps off Cuberos and grabs Natsu from behind, planning to crush him to the ground. Enraged that his plan failed, Natsu lets out a deafening scream that is heard throughout Nirvana. The scream affects Cobra differently due to his enhanced hearing and he falls to the ground while Happy grabs hold of Natsu.

Due to the effects of the poison, Happy's body begins to fail, causing him and Natsu to fall to the ground. Being on Nirvana triggers Natsu's motion sickness which, along with the effects of the poison, makes him incapable of moving. Suddenly, Cobra stands and prepares to kill Natsu for the pride of the Oracion Seis. Just as his attack is about to connect, Cobra is shot by Brain. Surprised by this betrayal, Cobra listens into Brain's heart finding out the Oración Seis leader thinks Cobra and the rest of the members weak for being defeated by a "common guild". Cobra then collapses from the injury, thinking of his prayer to listen to the voice of his one friend, Cuberos.

Aftermath
Seeing Brain betray Cobra, Natsu begins to get enraged. Brain tells him that he can make more comrades using the power of Nirvana. Natsu disagrees, calling those kind of comrades, puppets. Brain, impressed by Natsu's strength, then reveals his plan to make him his first puppet. Just as Brain begins to drag Natsu, Jura, Gray and Lucy arrive. A battered Happy explains the situation to them, saying that they should save Natsu since he's being taken away. Brain then tells the three his plan to make Natsu a part of a new set of Oracion Seis Generals, using the power of Nirvana. Refusing to turn evil, Natsu bites Brain who throws him aside. Due to the effect of his motion sickness, Natsu tells the others to defeat Brain and stop Nirvana.

Brain tells the group that it is impossible to stop Nirvana since it will shortly arrive its first destination, Cait Shelter. Surprised with the news, Jura demands Brain to tell them his purpose to attack the guild. Brain refuses, stating that he need not explain himself to them since he is the judge of light and dark. Enraged, Jura battles Brain, determined to find the purpose of his plan.