Biscuit Krueger

ビスケット=クルーガー, Bisuke, Biske

Bisuke is a 57-year-old woman who looks like a 12-year-old girl, and is a master and experienced teacher of Nen. She continues the Nen training Wing gave to Gon and Killua during the Greed Island arc. As a Treasure Hunter, Biscuit loves collecting rare jewels (and gets very excited about them; she has a habit of naming them) and getting money. Biscuit has a devious personality. She initially uses her cutesy appearance and demeanor to her advantage whether it's for information gathering, getting what she wants, or even in combat by acting innocent and helpless so most people will usually put their guards down around her. However, as a teacher of Nen, she has a stern and serious attitude towards her students.

Though in the beginning she was out to trouble Gon and Killua, at the end of the Greed Island arc she acknowledges (albeit, in her head) that she's close to developing parental feelings toward the two of them.

(Source: Wikia)