Cobra is a slim, muscular man of average height with tanned skin and spiky, upward-styled maroon hair; aside from a tuft covering his forehead and two bangs framing his face and purple slit-pupil eyes. He’s noted to have snake-like features, with slanted eyes similar to Natsu’s, a rather flat nose, and prominent canine teeth. Being an artificial Dragon Slayer, when Cobra makes use of his Dragon Slayer Magic, the tops of his hands and forearms become covered in crimson Dragon scales, while the bottoms are milky and smooth. His hands also turn into sharp, pointed, claws. After events of Nirvana, Cobra has a great burning scar over the half of his back and a scar from a bullet on his right shoulder, thanks to the Brain's betrayal. Also, after being imprisoned for seven years, Cobra gained a scar over his right eye, saying, that it's his sacrifice in order to attain new powers (the real reason of his scar appearing is unknown). His ears also became noticeably pointed (heavily hinted to his hearing powers upgrade).
Cobra's outfit consists of a black T-shirt with some strange end on it, and with a flame-like pattern, dark-colored pants with a scale-like pattern, a belt worn around the waist and usual dark-colored boots. Above his T-shirt, Cobra wears short red-colored jacket with a zipper and silver-colored edges. He also wears a white long coat with forest-colored fur and gray-colored stripes on it and a pair of dark-colored gloves.
Like the other members of the Oración Seis, Cobra is confident, sadistic and enjoys seeing his opponents suffer. Cobra believes that Second Generation Dragon Slayers are superior to First Generation Dragon Slayers, and even finds their existence questionable, as Dragons are believed to be extinct, and therefore finds it ridiculous that people such as Natsu were taught their Magic by nonexistent beings. He also seems to be quite easy-going and nonchalant, as he was able to laugh at a joke during a battle.
Cobra harbors great affection towards his snake Cubellios, considering her to be his greatest friend, and being willing to dedicate his prayer to hear her voice, which in itself is impossible, even for someone like Cobra, who has exceptional hearing. However, he does not know that Kinana is Cubellios herself.
In X791, at the time of his re-appearing, Cobra had a more quiet, angry, and hostile personality. He frequently belittled Erza Scarlet and the Fairy Tail Guild for their faith in friendship. He also experienced inner turmoil regarding the Reborn Oración Seis, and how much they had to give up; he believed that Fairy Tail is undeserving. It is not until he is defeated by Erza and he sees Kinana again that Cobra forgoes his forsaking of friendship and with that, he understands, that Kinana indeed his friend Cubellios Aside from Kinana whom he shares a strong bond with, Cobra seems to be quite loyal to his guildmates that originated from the Tower of Heaven as slaves, like him.
After some times passed and events of Grand Magic Games took a very dangerous side, as the dragons had appeared from the Eslipse Gate, by the Jellal's request, Lahar and Doranbolt set free Cobra in order to defeat Dragons. Cobra has displayed much more easy-going personality of himself at that time, as he again received the opportunity to hear all the voices and Kinana's too. He even saved the Blue Pegasus Guild and say to them to not interrupt his fight and disturb him. Even if he returned to the jail after the battle with dragons, it seems, that he indeed enjoyed the battle alongside the other Dragon Slayers.
Poison Dragon Slayer Magic: By having a Dragon Lacrima implanted into his body, Cobra obtained the ability to use this Magic. It grants him the power to produce poison from his body and to consume the one produced from external sources to heal and strengthen himself, which, as a result, grants him immunity from poison. The poison that he produces from his skin is so corrosive that it is said to be able to decay all that it touches, but can also act after a given amount of time: Cobra stated that its effects are first visible in a progressive weakening of the victim's body, which then results in death.
- Poison Dragon's Roar: Cobra's exclusive Dragon's Roar, incorporating the element of poison. Cobra quickly gathers and releases poison from his mouth in the form of deadly, poisonous stream that, when it makes contact with the target, injects a lethal virus into their body that slowly weakens them and restricts their movement before ultimately killing them.
- Poison Dragon's Twin Fang: Cobra moves his arms forward in a cross, forming a very large amount of poison in two massive waves shaped like fangs, which he uses to attack his opponents with great blunt force.
- Poison Dragon's Fang Thrust: Cobra generates a wave of poison, shaped like a large-fanged snake head, and sends it towards the target, stopping their incoming attacks by having the wave "bite" them.
- Poison Dragon's Spiral Jaw: Cobra jumps in the air and, when he is upside down, gathers poison on his legs and kicks the opponent while rotating. This spell is highly reminiscent of the Dragon's Claw Spells employed by several other Dragon Slayers.
- Poison Dragon's Scales: Cobra swings his arm, generating a very large number of scale-shaped masses of poison, which are rapidly sent flying at the target in consecutive reprises.
- Poison Dragon's Guard: Cobra moves his arms forward in a cross, creating a large shield of poison that defends him from the enemy's attacks, and, at the same time, gives him the opportunity to counter without fear of being intercepted.
- Poison Dragon's Crushing Fang: Cobra attacks with a poisonous open-hand, striking with his finger-tips from which poison mist trails.
- Poison Dragon's Grip Strike: Cobra grabs hold of his target with one hand and releases a burst of poison from it at point-blank range.
- Poison Dragon's Sharp Horn: Cobra punches his target then releases a burst of poison at point-blank range, which causes poison damage and burns.
- Dragon Slayer's Secret Art:
- Poisonous Mist: Death Trap: One of the trump cards, which Cobra has. Similar to the Roar Spell, Death Trap is a gas-like poison, which revolves around Cobra in big amount. While Cobra can freely control this spell, the mist itself has a high density and doesn't allow to see something in it. With it, the mist is also quite toxic, while the person, which caught up by this spell have only two choices - first is to not breath to save their life, second is to breath, but poison their body. Also, the poison, which mist consists in itself is very dangerous to breathing system of human's body. As a result, the longer person breathes the poisonous mist, the frightener are the consequences.
Sound Magic: Cobra has the uncanny Magical ability to hear a person's very soul, allowing him to tell if they are scared, what are they going to do next, and even allow him to hear their thoughts. This ability is so accurate that it was actually confused as mind reading. With it, Cobra was able to foresee all of the attacks performed against him and react accordingly, evading them without effort. His use of this Magic is so great that he was still able to counter each of Natsu's moves even when he tried to hide his thoughts. Though this only seems to work when the person's "voice" he is listening to is thinking, or has memories. The Magic can also act as a doubled-edged sword, as high pitched noises, such as Natsu's scream, can affect him greatly. By sacrificing his right eye's sight, he was able to use this Magic offensively, mostly by emitting strong sound waves.
- Sound Wall: Cobra manipulates the sound in his immediate vicinity into a wall of pure pressure, which simultaneously protects him and destroys portions of the surrounding area.
- Sound Palm: Through touch, Cobra transmits a very powerful sound wave from his palm to the target's body, sending them flying.
Enhanced Durability: Cobra has proven himself to be a very durable fighter: he has been seen enduring a barrage of powerful melee strikes from Natsu, enhanced by his Fire Dragon Slayer Magic, without receiving major injuries and continuing the battle afterwards as if nothing had happened. He also survived a fall of several meters which saw him coming crashing down to the ground, and stood back on his feet moments after.
Enhanced Strength: Cobra has displayed a high degree of strength: he is shown to be capable of effortlessly sending Natsu flying several meters away with seemingly casual attacks on two different occasions, the first with a simple slap, and the second with a knee. Cobra has also shown to be able, with his Dragon Slayer Magic, to completely crush the Rock Dragon's scales with a mere punch.
Master Hand-to-Hand Combatant: Cobra has been shown to be proficient in unarmed combat, employing fluent motions to rapidly strike his opponents. His hand-to-hand skills are complemented by a high degree of agility, with Cobra being capable of perfectly maneuvering and dodging attacks while remaining on Cubellios' back. The power of his strikes is greatly increased when he makes use of his Dragon Slayer Magic, which allows him to also poison his opponents on contact. Seven years later, Cobra's combat prowess has improved to a masterful level, as he is able to contend with an extremely unarmed combatant like Natsu Dragneel.
Immense Magic Power: As one of the six Dark Mages of the Oración Seis, Cobra boasts an immense amount of magic power. His Dragon Slayer Magic also increases his power twice it's original amount, making him as strong as an S-Class Mage. His magic color is violet-red.