By far the largest of the current Espada, Yammy Llargo is a giant Arrancar with tan skin and a ridge-lined cranium, brown eyes and black hair. He has long, bushy sideburns and a thin ponytail. Aside from that, he is bald. He also has orange eye brows and red markings under his eyes. He wears the standard Espada uniform, with the only difference being that his jacket is always open.

Like all Arrancar, he has a large hole in his chest signifying his previous time as a Hollow. What remains of his Hollow mask is the jawbone (complete with 8 teeth), which rests on his chin. A tattoo of the number 10, signifying Yammy's rank in the Espada, is on his left shoulder. However, in his released form, the number changes to 0.

Anger-Induced Physical Augmentation: Yammy is the only Espada capable of conserving his Reiyoku by sleeping and eating, this accumulation takes a considerable amount of time and inactivity. In doing so the reserves of power build up overtime and he can release his Resurrección causing his Espada number to changes and his true power is realized. As his anger increases so does his overall physical mass, allowing the instantaneous alteration of both his size and strength to greater levels.

    * Immense Strength: Yammy possesses superhuman strength of a level that his simplest actions cause destruction and damage. He easily is able to overpower Chad's initial "Brazo Derecha de Gigante" by effortlessly ripping his arm off completely and breaking it in two. He knocked Menoly aside a few hundred feet, breaking through the wall inside the dome of Las Noches by simply backhanding her. With minimum force behind it he is able to break through the walls of Las Noches.

    * Immense Spiritual Power: In his sealed form, Yammy's spiritual pressure is high enough to register as an Espada-level Arrancar, but not as high as the other Espada, due to his pre-released state.

Expert Hand-to-Hand Combatant: While not showing any technical of formal skill in hand-to-hand combat, Yammy relies entirely on a brawler style of fighting. Whether he possesses any skill in swordsmanship is unknown as he never uses his Zanpakutō in combat. His skill in hand-to-hand combat combined with his immense strength makes him a dangerous opponent.

Hierro is strong enough to resist an arrow from Uryū Ishida's recent bow, and survive the explosion of Mayuri's landmine with critical injuries. He is able to withstand Ishida's Sprenger technique with no real damage.

Cero: He can fire powerful red Cero blasts from his mouth, like many other high-class Hollows and Arrancar.

Bala: Yammy can also fire red Bala blasts from his fists, which are weaker than Cero blasts, but are also much faster. He is quite skilled at firing a multitude of these in quick succession.

Ira (憤獣 (イーラ), Īra; Spanish for "Anger", Japanese for "Angry Beast"): The handle is red and the guard looks like a rounded rectangle with two protrusions on each side.

    * Resurrección: Its release command is "Be enraged" (ブチ切れろ, buchikirero). When releasing his Zanpakutō explodes in release of spiritual power and Yammy grows to a monstrous size, reminiscent of the Japanese kaijus. His skull ridges become more pronounced taking on the appearance of two large purplish-gray head coverings extending to the back of his head. His white mask fragments fuse to his face, becoming his actual lower jaw. His red markings extend back from his face into two long flame tattoos. The majority of his body is tan in color, with his thin ponytail becoming longer. His body transforms drastically with his torso being largely the same but at the base attached to large elephant-like caterpillar-like legs, eight each extending back from the torso connected to the body at white carapace covered joints leading to up to the base of a bony tail club , similar to that of an Ankylosaurus. On each leg he has three large toes that extend back from the front to the back of the leg. He has five large black cylindrical tubes form on his back about half of the length of the tubes on his elbows. He has six black rounded nodules along the length of his forearms. Large purplish-gray cylindrical tubes form on his back and on his elbows, the latter of which can be used as piston-like rams. While releasing into this form his number changes from 10 to 0, by the 1 disintegrating leaving on the 0.

    Resurrección Special Ability: His physical abilities increase at an indefinable rate when released.

        * Cero: While in his released form, he is able to use a much more powerful Cero that he creates right in front of his mouth. Its range is extremely wide, in proportion with Yammy's increased size after releasing.

        * Enhanced Bala: Already demonstrating his ability to fire consecutive Bala blasts at the enemy, this skill is further improved. In his released form, this technique can easily hurl Ichigo away at a large distance, destroying part of the field of battle at the same time. It is proportionally bigger in accordance with Yammy's increase in size.

        * Enhanced Hierro: His Hierro is further enhanced in his form, as he seems to be totally unharmed after his fight against Chad, Rukia and Renji. He only received minor pain which he mostly ignored from a Kidō Spell, fired at point-blank range. Though somewhat dazed he survives with no damage a Cero he was still-charging that explodes in his mouth because of a Getsuga Tenshō Ichigo fires to counter it. When hit by a Getsuga Tenshō by Ichigo, with his hollow mask on, Yammy survived with a minor cut on his neck. He took a La Muerte attack to the face from Chad's "Brazo Izquierda del Diablo" with no damage.

        * Enhanced Strength: While in his released form, Yammy's already enormous strength further increases. He dispatches two of his opponents with presumably little effort. Yammy's strength is so immense that when he threw Rukia to the ground, she was unable to recover due to the air pressure being too hard on her body. He can bite through structures with ease. He effortlessly outmatched Chad's strongest attack using his "Brazo Derecha de Gigante".

        * Enhanced Spiritual Power: While in his released form, his spiritual pressure has explosively increased. Yammy states that amongst the Espada he is the strongest. He was able to use his reiatsu as a shield and expand it out as an explosion for a destruction that affected the surrounding area. His spiritual power is orange-red in coloration.

        * Enraged Form: Yammy explains that his release increases in strength the angrier he becomes. When Yammy's anger reaches a certain level, he can alter his Resurrección form, increasing his bulk. Upon taking this form, his damaged mask is restored and all previous injuries are healed. The black-piston like protrusions on his back become more like extensions of his vertebrae and he gains two massive horns on his back. He also gains multiple horns on his head including ones covering his lower jaw, as well as crack like markings framing his eyes. His arms are positioned in knuckle-walk position and his legs are hairy, ending with short, stubby toes; thus giving an ape-like appearance. His tail also becomes more hairy and ape like, losing its large club. His extra sets of legs are lost as well.

Byakuya Kuchiki is the 28th head of the noble Kuchiki clan, one of the four noble families in Soul Society. As such, Byakuya acts in an aristocratic manner: he is always quiet and apathetic towards other people.
In the ending of the second OVA, Sealed Sword Frenzy, he is even seen stepping out of a horse driven coach dressed in a suit, cane and top hat. Furthermore, the door is opened by a butler, showing his aristocratic status even when visiting the material world.
He claims that life in general isn't supposed to be entertaining, and in one of the omake chapters, he even makes up an idea for a game that isn't meant to be amusing. In spite of his icy and regal manner, Byakuya cares for and protects those important to him.

Byakuya is popular among the female shinigami of Soul Society, and was voted number one in the "captain we desire to release a photo book for" poll taken by the Shinigami Women's Association.
He likes Chinese bellflowers, night time walks, and spicy food.

Byakuya wears the standard captain uniform along with a white headpiece called a kenseikan (symbolizing his noble rank as the head of the Kuchiki family) and a white scarf made by the master weaver, Tsujishirō Kuroemon III. The scarf is made from silver-white windflower light silk (ginpaku kazahana no uzuginu) and is a family heirloom handed down through the generations to the head of the Kuchiki family.