I intended to just sketch this...oops.
Inspiration: I always thought Amaimon kind of reminded me of a stupid young fox, the type in fiction who would slaughter a whole chicken coop just to rip them to shreds for fun. Someone on tumblr replied that they thought Mephisto would be a cunning fox; an idea was born.
SAI + Photoshop CS6.
Textures used: [link] [link]
Ao No Exorcist (c) Kazue Kato.