Tu Oderschvank, Nelliel

ネリエル・トゥ・オーデルシュヴァンク

Neliel Tu Oderschvank, commonly known as Nel Tu, is a good-natured, child-like Arrancar when first introduced. The remains of her hollow mask make up a cartoonish skull on the top of her head. Nel and her companions believe Soul Reapers, not hollows, to be evil, and as such are afraid of them. In spite of this, she develops an attachment to Ichigo Kurosaki and starts following him around after her introduction. She often mispronounces Ichigo's name as 'Itsygo' due to her lisping, and she is a self-proclaimed masochist.

Spoiler

Nel's true form is that of a fully-grown woman, her mask appearing less cartoonish with a pair of curved horns. A large "3" tattooed on her back indicates that she was previously the Tercera Espada.
Tired of her superiority over him, Nnoitra Jiruga snuck up on and attacked Nel from behind with the help of Szayel Aporro in the past, managing to crack her mask, causing her to turn into her child-form, giving her amnesia, and allowing him to expel her from the Espada. When Nel runs into Nnoitra years later as he begins to torture Ichigo, she turns into her adult form with her memories restored. Though considerably more mature than her child form, she retains her child-like voice and affection for Ichigo, as she comically hugs him without realizing that her strength is causing him personal injury. As she is about to defeat Nnoitra, Nel reverts back to her child form, losing all of her adult powers. Later on, Urahara enables her to maintain her adult form permanently. She works with Harribel and helps her to rule Hueco Mundo in the wake of Yhwach's invasion.
In her child-state, Nel's vomit (which she believes to be saliva) acts as a rather weak, but useful, healing agent. In both her child and adult form, she can swallow cero attacks and fire them back. In her adult form, she can also add her own cero to this blast, doubling its power, aptly named a "cero doble". Nel's zanpakutō, which manifests when she transforms, is named Gamuza (羚騎士（ガミューサ）, Gamyūsa, Spanish for "chamois," Japanese for "antelope knight"). Her released form is that of a ibex-like centaur with longer curved horns, a thick tail, and armor over her shoulders and hands. Her sword transforms into a double-ended white lance, giving her the appearance of a medieval knight or a jouster. One of her attacks in this form is called Lanzador Verde (Spanish for "green lancer"), in which she throws her lance directly at her opponent. The lance moves at high speed and rotates extremely fast, drilling through anything it hits.