Stark has blue-gray eyes and wavy, dark brown hair, which ends at the base of his neck, is always unkempt, and is parted down the middle. He has a faded goatee. His clothing is typical of an Arrancar: he wears a white jacket outlined in black, though altered with the collar upturned. A black sash is worn in a manner similar to a matador around his waist and he wears white gloves. The remains of his Hollow mask consist of a fanged bottom jaw which is positioned along his neck. His Hollow hole is on his sternum, right below the tip of his mask. His Espada tattoo is featured on the back of his left hand, which he conceals with his glove.
Stark is a lazy and unenthusiastic man who spends much of his time asleep, and no one, except Lilynette Gingerback, his other half, appears to try and stop him from doing so. Despite being the highest-ranking Espada, he is not eager to take a leadership role, allowing Baraggan Louisenbairn to take over at the battle of the Fake Karakura Town. He is not particularly interested in whatever is going on around him, though he is observant and a capable analyst. Unlike many of the Espada, he is not inherently violent or overly arrogant, which explains why he is different from the rest.
Prior to meeting Aizen, Stark hated the loneliness he felt in the world but often could not avoid it because his mere presence killed off others around him. He envied the weak and wanted to be like them because they could travel in groups. Eventually he felt so lonely that he divided his soul into two separate beings to escape his solitude. From there he continued to search for friends until he met Aizen. Despite having gained many comrades after joining Aizen, he rarely directly addresses any of them other than Lilynette.
He initially does not seem to care a great deal for his fellow Espada, showing no visible signs of distress or concern. When he learns of Aaroniero Arruruerie's death, he lazily states there is nothing he could do about it, and when Baraggan and Tier Halibel are apparently overwhelmed by their opponents' respective Bankai, he only asks Shunsui Kyoraku if all the captains' Bankai are so powerful. However, this indifferent attitude seems to be dispelled with Baraggan's death. Stark states Sosuke Aizen not sparing even a word for Baraggan is horrible. Stark himself is notably affected by this turn of events, being drained of his motivation to fight. After arguing with Lilynette for a while, he states he is not the type for revenge, but his desire to not see any more comrades die proves to be enough motivation for him to keep fighting. Starrk seems to be opposed to the notion of killing people, offering Love Aikawa and Rojuro Otoribashi a chance to run away instead of finishing them off.
Stark often ends up in situations with him on the receiving end of physical abuse from his partner Lilynette, even though he does little to stop her actions. He can be serious on occasion, although his personality does not change much: he comes off as reluctant, but nonetheless willing to complete the task at hand. Such is the case when he was ordered to take back Orihime Inoue, despite saying he abhors such a strategy. He is fairly similar to Shunsui in personality, something Starrk himself acknowledges.
Soul-Seperation: Stark has the unique ability to separate his soul due to his immense spiritual energy. His spiritual energy splits and turns itself into another being, which reacts to his spiritual signature.
Master Swordsman Specialist: Stark is extremely well versed in sword fighting, contrary to what his laid back and careless demeanor would suggest. Despite not having been formally trained, save for a few basic lessons from a Zanjutsu master, Sosuke Aizen, Stark's basic skill alone is capable of contending with the likes of most other sword fighting masters. It was good enough to contend with Shunsui Kyoraku, who was often revered as an extremely talented sword fighter in his own right, using only a single sword in comparison to the latter's two. Even when the two of them reached an initial stand still, both fighters concluded that neither of them were truly trying. Fighting with a more defensive and composed style, Stark's moveset centers on staying on the defensive until an opponent's pattern begins to sink in and become more apparent. Only then will he start looking for openings to strike out at his foe with a strong and well placed slash or stab. While fighting, Stark employs a string of dynamic footing to attack from several well placed angles. This, coupled with his Spiritually enhanced strength, makes his ability in swordsmanship match that of any opponent that he may come across, be it from a Captain-level opponent to beyond. The true extent of his swordsmanship has yet to be truly seen, but it can be safely assumed that he can easily battle on par with Captain-level foes with very little effort. When he enters his Released state, Stark's swordsmanship skill is instead traded for his tremendous marksmanship. However, his sword fighting skill is not entirely forsaken, as he is capable of manifesting two energy blades from his bandoliers by using the ability "Colmillo". Here, his style changes into a more relentless and suprise based pattern, striking the foe with several sword swipes and giving them hardly any time to react or dodge appropriately.
Master Marksman Specialist: When firing his Cero, Stark has been noted to have rather keen accuracy, almost always hitting his foe unless they are moving at great speeds. They are noted to almost always hit their mark, obliderating whatever lies in their path directly. Even when he isn't looking, such as firing the blast from his back or another location, they rarely miss their desired destination. Shunsui had a particularly difficult time managing Stark due to the sheer potency and accuracy of Cero's that the Arrancar sent his way. Once Stark dons the Released form of Los Lobos and acquires the dual pistols granted to him with said transformation, this particular talent becomes all the more apparent. Firing his weapons at blinding speed, the Cero blasts are said to be so quick and deadly that the foe never has the chance to see them coming, being struck in their central, most weakest points and being utterly blown away. Every shot that he fires lands somewhere and, as Lilynette puts it: "Screws someone's day up."
Sonído Master: Stark's skill and speed in Sonído is so great, it seems as though he possesses a form of teleportation, simply appearing solidly instead of shimmering for a second like other Sonído users. He avoided both Kenpachi Zaraki and Ichigo Kurosaki in order to recapture Orihime Inoue, returning her to Sosuke Aizen within an instant. His proficiency with Sonído allows him to create multiple after-images of himself to confuse the enemy. He surprised Jushiro Ukitake by appearing next to him after dodging an attack faster than his own post-release Cero. He also evaded various attacks by the Visored Love and Rose, along with attacks from Shunsui while fighting them.
Cero: His Cero is blue in color. While a standard ability for Arrancar, Starrk's abilities with it are very unique. As noted by Shunsui, unlike other Arrancar, he can apparently fire a Cero without a "fighting pose", meaning he can fire it without any warning from body gestures. Stark can charge and fire it rather quickly, leaving even less time for his target to react. He can fire his Cero from various points on his body, such as from either hand, his chin, and his chest.
Immense Spiritual Power: As one of the top four Espada, Stark is possesses tremendous spiritual power, which made him forbidden to release in Zanpakuto within the bottom canopy of Las Noches, since such power could destroy the fortress. His Reiatsu is blue. Prior to meeting Aizen, his spiritual power was unintentionally killing other Hollows just by being near them, even after splitting his spiritual energy.
Highly Perceptive Combatant: Stark is very detail-oriented when it comes to fighting. He notices his opponent's mannerisms, and discerns the reasons behind those actions and the weaknesses and strengths of his opponent. He can look at unfamiliar attacks and figure out how they work by just viewing them once.
Los Lobos (Wolf Pack): Unlike all other known Arrancar, Stark's enormous power is not sealed in the form of a Zanpakuto. Instead, it is sealed in the form of another Arrancar, his own subordinate, Lilynette Gingerback, who, while a separate, distinct being, is an actual part of him.
- Resurrección: Los Lobos' release command is "Kick About", relating to the aspect of Wolves for which it is named. When these words leave his mouth, his sword practically explodes in a vibrant display of white blue spiritual energy. Manifesting like a wildfire, the energy released from this transformation spreads for several meters upon release, burning and corroding anything and anyone in it's wake. However, despite this, the energy feels surprisingly cold, distant, and forlorn, much like that of Stark's very existance. It can make his opponent's feel that same sense of depression that he had gone through all those years ago. Only now, they are facing the wrath of what such a feeling would cast upon them. The bluish white fire slowly clears into a faint trail of cyan smoke, cold and eery, like the atmosphere in where they reside. Stark is revealed to be sitting down atop the clouds within the smoke, his reluctance in releasing such a power revealed before all who have been foolish enough to come across him. Standing up slowly, most always with a sigh or exhale of cold breath, Stark's attire is revealed to have changed into something that would draw the eye of any. When released, he wields two ornamental pistols, each of them the same length. These pistols are actually Lilynette, for both pistols appear to house her body as well as her consciousness. She can speak through both pistols, and retains a sense of feeling via outside stimulus. Part of Lilynette's mask appears on his head, stretching from the back of his head around to the eyepiece on his left eye, with the flame pattern changing to emerge from the eyepiece and follow the mask fragment around to the back of his head. The mask itself is connected by two chains around his right eye. His Arrancar outfit changes drastically as well: his upper body is covered in a gray fur-lined jacket over a double-breasted vest, while his legs are covered in dark, skin-tight pants, with gray knee-high fur leggings covering his lower legs, and his arms are covered in gray, elbow-length fur armbands, which end at his wrists. There are ribbon-covered bandoleers emerging from his upper back and disappearing into his upper forearms. With fur-covered holsters, Starrk's released form resembles a Wild West gunslinger.
Resurreccion Special Ability: Stark's released form grants him new abilities and enhances his existing ones.
- Enhanced Strength: While in his released form, Stark is physically enhanced to the point where he can parry a powerful technique from Shunsui.
- Enhanced Hierro: Stark's Hierro is enhanced in this form. After taking a direct hit from Love's immense Shikai, Tengumaru, and being sent crashing into the town below, Starrk ended up lying practically unharmed among the rubble while uttering only a halfhearted "ow" in response to the attack.
- Enhanced Cero Firing: Stark can fire Ceros from his dual guns. He claims that he can fire up to 1000 of these Ceros at once.
- Cero Mertalleta (Infinite Ammunition Hollow Flash): Stark uses his pistols to simultaneously unleash a powerful barrage of Ceros which, because of their density and grouping, appear to fuse together into one large Cero blast. He can change the direction of this attack while firing, making it extremely difficult to avoid.
- Colmillo (Fang): Stark can summon spiritual energy swords from his bandoleers, which vaguely resemble the ordinary katana he wields in his sealed form, but with four curved prongs hanging off of the guard. He uses one, then two swords to combat Shunsui's dual-blade Shikai.
- Camarada (Soul Brethern/Compatriots): Stark can summon a pack of flaming grey wolves, seemingly numbring in the hundreds. The wolves are controlled verbally by Starrk, and will chase down the enemy with the intent to cling via a bite. Upon biting the enemy or getting close enough, the wolves erupt in explosions of varying size and power. They can be very destructive; when one exploded, it destroyed a large area of the Fake Karakura Town in a huge explosion, which dwarfed the surrounding buildings. Starrk can summon them without limit, thus overwhelming the enemy with their sheer numbers. These wolves are pieces of both Starrk and Lilynette's soul, which they can split apart and control in battle. Love states that they are like flames, for they reform from any harm done to them to continue their attack without pause. The two bandoleers on Starrk's back are the source of the wolves. This ability fuses him and Lilynette even further, for the pistols disappear and she becomes a presence in his body, allowing her to speak through him. However, the wolves possess a critical weakness; they can only harm any objects they have bitten before exploding, so if they are forced to explode by a mid-range attack like Bushogoma, the opponent is protected from the blast. Additionally, if Lilynette's soul is in the wolves that are detonated in this way, she will die.
Sword: While having no special properties, Stark wields a standard-sized katana. He uses it as a weapon in his pre-released state to make up for not having a standard Zanpakuto. It sports a pewter-colored rectangular guard, with small protrusions on each corner, and a sun-like design wrapped around the hilt's collar. The hilt itself is a yellow color, and the sheath is a metallic-gold color.
- Lilynette Gingerback (Other-half and subordinate)