Amadeus

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. 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 effects his social life).