Mephisto Pheles (メフィスト・フェレス Mefisuto Feresu), whose real name is Samael (サマエル Samaeru), is an Exorcist and the second strongest of the Eight Demon Kings; he holds the title The King of Time (時の王 Toki no Ō).[1] He uses the name Johann Faust V (ヨハン·ファウスト五世 Yohan Fausuto Gosei) in public and is the Principal of True Cross Academy.[2] Following the death of Shiro Fujimoto, Mephisto takes it upon himself to enroll Rin in True Cross Academy.

Mephisto has dark purple hair and forest green eyes. He is also very tall, having a height of 195 cm (6'5"). He is usually seen in an elegant white outfit that consists of a white top hat with pink and purple around the base, purple gloves, a tie that is pink with white dots, a white suit-shirt and undershirt, jester-style pants, and pointed shoes. His appearance prompts Rin to refer to him as The Clown. As the series progresses, he stops wearing the jester pants and pointed shoes, instead wearing white dress pants and black shoes.

In addition, he can transform into a small white dog when he counts down from three in German (up to three in the anime). In this form he is a small, fluffy, Scottish terrier-looking dog with a large pink ribbon around his neck with a silver trinket attached to it, the trinket being the symbol of an Exorcist. He also is shown to be able to transform into a Bug.

Shrouded in mystery, one quickly learns of Mephisto's innate ability to act as if he knows more than what he is letting on. Careful and meticulous, he is like a chess player, always ahead of the game.

He enjoys chaos, as he stated to himself that he was a hell-raiser, and Assiah to be his playground. He frequently observes the growing conflict around Rin and his friends with delight, though he does not wish to see any of his students get killed.[5] He apparently 'loves' humans. When Mephisto first meets Amaimon in the series, it is implied he is conspiring with Satan and is most likely training Rin on his orders. He likes to make gambles with whoever possible, including Fujimoto, Rin, and the True Cross Order.

He is prone to eccentric moments nestled in between serious moments, making light of a heavy mood and is portrayed as a man with more money than sense, but is very cheap when it comes to spending on others. Like his brother, he loves to eat sweets and he is deeply interested in the Japanese pop culture, proudly stating that he is an otaku (that is, loves computers, anime/manga, and/or pop culture to the point that it negatively affects his social life).

According to his own words, Mephisto has wandered Assiah for an unknown amount of time. He has apparently been known as Loki, Trickster, and Raven at some point during that period of time. Around 200 years earlier he became known as Mephisto Pheles. Other than the fact that he was close friends with Shiro, and that he has assisted the Vatican for around 200 years nothing much is known about him.