Jak is a Elf-Human male with green-blond hair, cerulean blue eyes, and fair skin. Jak changes notably as a character over the course of the series. He is presented as brave and curious, willing to step into dangerous situations given the need. The most notable feature of his personality in the beginning was his apparent mutism. When the first war struck, he breaks away from his mutism, and after being subject to dark eco treatments for two years at the hands of Baron Praxis, his main basis becomes revenge, and he became angry and reckless—this is exacerbated by the presence of dark eco in his body.