Rak Wraithraiser

Rak Wraithraiser (Korean: 라크 레크레이셔; RR: Rahk Rekraisher) is a large, powerful, and very confident spear bearer. He unwillingly teamed up with Twenty-Fifth Bam and Khun Aguero Agnis early in the story, and he quickly became attached to them during the following tests. Due to his reptile-like features, he is sometimes referred to as "Alligator" or "Gator" and even "Crocodile". Rak refers to his friends and people he meets as "turtles" of different colours and features (ex: black turtle, blue turtle, crazy turtle); the term by which he also earnestly addresses his "prey".

Rak is able to change his size so that he is smaller and convenient to walk around because he is a Compression Lisensor which gives him the ability to shrink his size at will so he can move around the Tower more easily.

(Source: Wikipedia)