Ulquiorra Schiffer bio/outline...

Ulquiorra is a male arrancar with a melancholic appearance and has green eyes with slit pupils. He has cyan lines descending from his eyes, making it appear as if he is crying, and is almost always frowning. He wears typical arrancar clothes: a white jacket, black sash, and a white hakama; however, his jacket has longer coat-tails than others. Like most other arrancar, he possesses remnants of his former life as a hollow in his appearance. In his first appearance, Ulquiorra's hollow hole is positioned at the base of his neck, but when Ichigo encounters Ulquiorra in Las Noches, it has been moved onto his chest. The remainder of his hollow mask lies on top of his head, forming a broken helmet, much like that of the example silhouette of a vasto lorde. His Espada number, four, signifying his rank amongst the Espada and level of power, is tattooed on the left side of his chest. Ulquiorra's name meaning in english is unknown, however, his last name which is Schiffer means "Sailor" in German. This still doesn't give any hints of what his true form may look like.

Ulquiorra is a very cold and callous figure, hitting his comrade Yammy in the stomach with his arm on one occasion in an effort to get his attention. Furthermore, he displays extreme disinterest in the greater portion of his battle, tending to keep his hands in his pockets while he fights. He also deems anyone he does not find of particular interest to be "trash" and therefore expendable. As noted by Grimmjow Jeagerjaques, Ulquiorra has a habit of stabbing people in the same location as his hollow hole whenever he's particularly interested in a battle. Whether he is consciously aware of this habit or not is unknown.

Ulquiorra is also analytical; during his and Yammy's first visit to the human world, he makes several remarks on the humans who confront them. He theorizes that Orihime Inoue's healing power is a temporal-spatial ability, which Aizen describes as the rejection of fate, and comments on how Ichigo Kurosaki's bankai can easily get through Yammy's defenses. He also notes Ichigo's power fluctuation, which varies between very weak to stronger than his own.

It would appear that Ulquiorra and Grimmjow, the 6th Espada, are not on good terms. While Ulquiorra allowed Yammy to kill anyone he deemed as "trash", which included Ichigo, Ulquiorra allowed him to live based on his belief that Ichigo's power was so turbulent that eventually he would destroy himself. Grimmjow's conflicting viewpoint was that Ichigo should have been destroyed outright, as he could overcome his weakness and grow even stronger. Despite Grimmjow's argument, Aizen trusted Ulquiorra's judgement.