|Base of Operations||Las Noches|
Ulquiorra is a slender, yet fairly muscular, male Arrancar of average height with a melancholic appearance. He has fairly short, messy black hair, pale white skin, a black upper lip, and green eyes with small slit-shaped pupils, similar to a cat's. Part of his bangs falls between his eyes, and he has distinctively thick eyebrows. He has teal lines which descend from the lower part of his eyes. His facial expression rarely changes, though he is almost always frowning. He wears typical Arrancar clothes: a white jacket, black sash, and a white hakama. However, his jacket has longer coattails than others, and the collar is higher.
Like most other Arrancar, he possesses remnants of his former life as a Hollow in his appearance. His Hollow hole is located on his sternum, though the hole was initially located on the base of his throat. The remainder of his Hollow mask lies on the top-left side of his head, forming a broken horned helmet. His Espada tattoo lies on the left side of his chest.
Ulquiorra is callous, dispassionate, aloof, brooding, and indifferent. He also believes (or used to believe) in the concept of materialism, claiming that something cannot exist unless it can be physically seen and/or touched. Because of this, he does not believe in the notion of things such as love or "heart". This is all likely a reflection of his Aspect of Death, Emptiness. One of Ulquiorra's most prominent traits is his curiosity, as when something piques his interest, he will analyze and study it to the point of even showing a willingness to defy direct orders from his superiors.
Ulquiorra will not hesitate to harm anyone, even comrades, if they get in his way or if he believes that it is necessary. Despite this, he is not overly violent or belligerent. He is also very cunning and analytical. Also, despite keeping his anger in check most of the time, he is capable of feeling frustration whenever his enemies make a fool of him or he is presented with something that he cannot understand.
Ulquiorra was initially a Vasto Lorde, the highest level of power a Hollow could achieve. He preferred solitude, or perhaps was exiled by a clan of Hollows he belonged to, and would often wander Hueco Mundo searching for nothing and yet moving along anyway. During one of these walks, he found a single, solitary white tree with a hollow center, and came to feel that it was similar to him. Climbing inside the tree, Ulquiorra sealed himself inside and finally felt at peace.
An unspecified amount of time later, Ulquiorra was turned into an Arrancar by Sosuke Aizen and joined his elite soldier group, the Espada, becoming the Cuarto (Fourth) Espada at some point (it is unknown if he ever had a lower rank or was immediately made the Cuarto upon being turned into an Arrancar). At some point, Ulquiorra unlocked a second stage to Resurreccion, the Segunda Etapa, an achievement that would have likely resulted in his promotion to Primera (First), or perhaps even Cero (Zero), Espada, but for an unspecified reason, he kept the form a secret, even from Aizen.
- Ulquiorra's Aspect of Death is Emptiness.
- In both timelines, Ulquiorra teaches Harribel, Nelliel and Starrk how to achieve Segunda Etapa form.