Jellal is a tall and well-defined young man whose most prominent features are his blue hair that is long and shaggy, and a red tattoo above and under his right eye, which he has had since his childhood. His dark blue, guild mark is located on the back of his right hand.
Jellal's attire currently consists of a long dark coat (very similar to the one he stole from the Naked Mummy member), decorated by golden trimmings, white bands around his arms, and heart-like designs running down the sleeves and sides of the coat. Beneath this, Jellal wears plated armor, which covers his abdomen, along with a tight-fitting shirt designed for his Meteor spell underneath, and dark pants bearing the symbol of Crime Sorcière with a pair of high-calf dark boots. On top of all this, Jellal sports a dark blue long cloak with a hood to conceal his identity.
When he was young, Jellal was a kind, compassionate boy, and cared deeply for his friends. He was always cheerful and optimistic, despite his disposition as a slave. After a failed escape attempt, he readily accepted punishment in Erza's stead, and never once lost his faith in the thought of being free. Later, as he was manipulated by what he thought to be Zeref's ghost, he drastically changed: Jellal became obsessed with the idea of building a new R-System and treated the slaves much better — to the extent that they didn't even think they were still slaves. But through this method of treatment, they did more work, which was Jellal's ultimate reason for treating them as such in the first place. He sees his actions as a game, even if said game results in the loss of lives, his very own included.
After he was revived by Wendy Marvell, he suffered from amnesia and seemed to be somewhat afraid of the world. Though not remembering his own identity, he remembered the names Erza and Natsu Dragneel's names, respectively. As he learned of his sins, Jellal wished to die, as he believed it to be his only form of atonement, but Erza convinced that through living, he can find a way to make up for his past horrid deeds. Following these instances, even when arrested by the Knights and knowing he would be given the death penalty, Jellal remained calm and even happy, just as he did when he was a child. Mavis Vermilion even commented that Jellal possesses the same "heart" as those in Fairy Tail, in spite of the fact that he isn't an actual member.
Seven years later, after regaining his memories and having returned to his original personality, Jellal is now a calm, mature, intelligent, and kind individual. He has shown a cheerful side, as he often smiles when pleased, or when his friends are happy. While as "Mystogan", he makes sure he acts quiet and aloof, so as to not arouse suspicion to the fact that Fairy Tail is housing an escaped convict. However, Jellal's regret towards his past deeds have caused him to feel the need to atone for his sins, which he did by creating Crime Sorcière: an Independent Guild dedicated to the destruction of Dark Guilds. Despite this, he still feels he deserves punishment, as he told Ultear and Meredy that "punishment" is the theme of their guild. It is this guilt that keeps Jellal from expressing his love for Erza, which she reciprocates, as he believes he doesn't deserve her. However, he eventually accepted his love for her after the arrival of their future daughter, and how much Erza loves him.
Despite his rather serious nature, Jellal does have a comedic side, as in his fight with Jura Neekis, where (as a direct result of Ultear and Meredy sabotaging his battle with the Wizard Saint) he has fits of hysterical laughter, as well as reacting strongly to the sensation of peppers he had in his mouth. Later, when he walked back to his teammates, Jellal felt ashamed, and stated that he had no words to describe his feelings of shame and embarrassment.
Heavenly Body Magic: It is a powerful Magic based around astronomical objects, such as meteors, stars and black holes. Jellal generates and manipulates the energy of stars from his body and uses it against his enemy. Jellal has shown tremendous mastery over this particular form of Magic. The properties of Heavenly Body Magic rely primarily on astronomical objects like meteors or the generation and manipulation of the energy of stars from their own body. Jellal can create powerful light blasts or beams of high destructive power, reminiscent of starlight, at his opponents, or engulf his fists in light to enhance the blows of his punches for melee combat. This light is not the only substance used, however. He is also capable of using the power of gravity against the opponent for destructive usage; the strength can be comparable to the effects caused by a crushing meteor. The use of such Magic can be used to enhance Jellal's own skills drastically for various purposes, such as shrouding him in Magic that can increase his speed significantly. However, it appears that he requires a special outfit to wear in order to manipulate the Magic for such a purpose.
- Meteor: Jellal's body is surrounded by a cloak of Heavenly Body Magic, allowing him to move through the air at incredible speeds, almost surpassing the speed of light. Even if someone could detect his trajectory, it is nearly impossible to catch him. With his speed, Jellal assaults his opponents with quick, but powerful, melee attacks. Jellal wears a special suit under his robes to better utilize this particular spell. During Jellal's battle with Jura Neekis, the speed granted to him by Meteor amazed even Jet, a Mage specializing in speed-enhancing Magic.
- Heavenly Beams: A spell in which Jellal releases several powerful beams from his hands towards his opponent, causing great damage. Upon casting it, Jellal is able to control the direction each beam takes and their power.
- Heavenly Blast: A spell in which Jellal closes his fist, except for two fingers and swipes them backwards; a large sphere of Heavenly Body Magic appears and rushes towards his target. The blast is powerful enough to dealt massive damage to its surround as it sent all of its targets flying meters away.
- Heavenly Palm: A spell in which Jellal grabs his arm with his other hand, and straightens his palm; a ball of Heavenly Magic appears in his palm, which then is shot at the target, pushing them away as if it were an invisible wall. It is similar to breaking the air itself as Jellal was able to create waves on the ocean by executing this attack simultaneously.
- Heavenly Breakdown: A spell in which Jellal swipes his hand, causing the ground in front of him to break, making everything on top of it fall. Jellal can extend the area of the explosion by increasing the amount of power in the spell, and can even change the area that will explode.
- Heavenly Arrows: A spell in which Jellal swipes his hands, releasing several arrows of light towards his target. Once released, Jellal can send the arrows in different directions, this is quite helpful since he can put the amount of power he wants, with this he can hit different targets at the same time.
- Grand Chariot: While in the air, Jellal places both arms on top of each other, with the top hand having only the index and middle fingers spread out. Seven Magic Seals are then summoned in front of him and connect, creating a constellation of sorts. Each Magic Seal then releases a powerful light blast down on the opponent, forming the same pattern on the ground before exploding. According to Jellal, this spell's destruction capability rivals that of an actual meteor.
- Altairis: Jellal crosses his arms above his head to begin casting the spell. As he prepares to fire the spell, all nearby shadows are drawn towards him, forming a small black orb which rapidly grows in size (inside are small white lights, giving it an appearance similar to that of the night sky), before unleashing it towards the target. The orb appears to be incredibly dense, and may hold a tremendous amount of gravity capable of crushing everything in Jellal's path. This spell was used when Simon saved Erza.
- True Heavenly Body Magic: Sema: An attack in which Jellal bows down and points his hands downwards, with all the fingers closed except the index and middle fingers. He then begins to slowly move his right hand until it points upwards, causing the clouds above Jellal to begin circling, creating what appears to be a cyclone. From the center of the swirling formation, a glowing orb begins to form, growing in size until a humongous meteor emerges, falling quickly to earth towards the intended target. When the meteor hits, the force is strong enough to create a large explosion, which engulfs a wide area and releases a strong hurricane of air, also leaving a large crater in its wake.
Darkness Magic: Jellal, due to his "possession" at the hands of "Zeref", is an expert in the usage of Darkness Magic. He was shown using almost exclusively this form of Magic for all of his fight with Erza, in which he proved himself capable of creating the ghostly entities characteristic of this form of Magic, using them to both hit and immobilize the woman with great skill. In addition, as a child, he could employ Darkness Magic in other, more unusual ways. Although he would never use this magic after becoming good again, he would only use this magic if someone hurt the people he'd care about, namely Erza and his future daughter.
Expert Hand-to-Hand Combatant: Jellal, despite favoring the use of his ranged Magic, has shown himself to be a capable unarmed combatant: while his speed was enhanced by his Meteor spell, Jellal went on to attack and brutally injure Natsu Dragneel several times with strong melee attacks, such as punches and kicks.
Expert Swordsmanship Specialist: Despite having scarcely been shown employing one, Jellal, much like his childhood friend Erza Scarlet, has proven himself able to wield a sword with impressive proficiency since his younger years: during his time as a slave in the Tower of Heaven, he was shown to be capable of reaching the cell Erza was being kept prisoner in by himself, having dispatched all of the guards there with a massive sword he had taken from one of them.
Tremendous Magic Power: Jellal has been shown to possess a vast amount of Magic Power, enough for him to be made a member of the Ten Wizard Saints, a group containing some of the strongest Mages in Earth Land, as well as a member of the Magic Council, the ruling body of the Magic world; the latter in spite of both his young age and his overbearingness towards older, fellow councilors. Such feats were made more notable by the fact that the one receiving such titles wasn't actually him, but rather the persona he had created with his Thought Projection, Siegrain, which required a considerable amount of Jellal's own Magic Power to be kept active. Jellal also possesses masterful control over his magical energy, able to hide his presence and make his opponents of S-class and below level sweat in fear. His magic color is golden-yellow.
Immense Durability: Jellal is a highly resilient opponent, who has proven himself capable of undergoing large amounts of damage without collapsing: during the events of the Tower of Heaven, he could continue fighting after being slashed by Erza Scarlet (despite such action having later stopped him from casting Abyss Break), and receiving a barrage of Fire Dragon Slayer Magic spells from Natsu Dragneel, emerging unscathed from them; later on, most importantly, he was able to survive Natsu's attacks after the latter had entered Dragon Force, even after being sent crashing down through his own Tower of Heaven. He was also able to fuse his body with the Etherion and attain control of it, something which should have resulted in his certain death. He, however, yet again survived, entering a comatose state, from which he was awoken via Wendy Marvell's Sky Dragon Slayer Magic. He can even withstand high-caliber bullets, powerful magic blasts, immense physical punches and kicks, and even crashing from great heights, all without sustaining any serious damage.
Immense Agility: Aside from his Magic capabilities, Jellal is fast, agile, and has quick reflexes, being shown avoiding and redirecting the slashes from Erza's large bladed weapons with ease, reacting to them with his own Magic. He was also shown evading the assaults from Jura Neekis' stone pillars through several remarkable acrobatic leaps.
Enhanced Strength: Jellal has displayed considerable physical strength, enough for him to send a man of Deathwing's stature flying several meters away from him using a single hand.
Enhanced Endurance: Jellal's vast array of spells comes with the stamina to employ them in subsequent reprises, with him being resilient enough to use Flame of Rebuke, a spell powerful enough to allow Natsu Dragneel to enter Dragon Force, replicating the effects of Etherion, the ultimate weapon of the Magic Council, after attempting to cast a Self-Destruction Spell on both Nirvana and himself, something which greatly weakened him.
Keen Intellect: Jellal is a smart, cunning and resourceful individual who displayed particular skill in deception, having been capable of fooling both Erza Scarlet and the entirety of the Magic Council, even managing to become a member himself. He has shown himself capable of creating clever schemes and planning ahead, being the schemer of the plan to revive Zeref, whom he believed dead, and tricking the Council into unintentionally working for him. Jellal's natural cleverness comes with a vast knowledge and deep understanding of the Magic world, with him being aware of powerful spells such as Unison Raid, and, thanks to his time in the Council, possessing thorough information about the ancient Magic Nirvana, even knowing where it was hidden and how to unseal it.