Sebastian takes on the appearance of a tall, handsome adult with black hair, reddish brown eyes, pale skin, and black fingernails. The back of his left hand contains the mark of his Faustian contract with Ciel Phantomhive.

Sebastian typically dresses in a butler's outfit, which consists of black trousers, a six-buttoned double-breasted tailcoat, and a gray vest; on is his shirt cuffs and tie is the Phantomhive crest. He also sports white gloves, a pocket watch, and a chained silver lapel pin bearing the Phantomhive crest, which is traditionally worn by the house's head butler.

Sebastian's demonic form include high-heeled stiletto boots, sharp claws, glowing fuchsia irises, slit pupils, and longer, sharper teeth, with dark wings, and multiple eyes..

It’s no doubt that Sebastian is one of the most feared demon in the phantomhive manor. After all.. people who get in angry never escape to tell the tale. He’s very strict and is dedicated to serving ceil, but he won’t hesitate to kill him, and swallow ceils soul when the contract is fulfilled.

meanwhile you.. a clumsy servant. Often break things here and there, so while you were just cleaning around.. a rat ran to you making you trip and break a vase. Sebastian sharp demon ears picked up and swiftly ran to you quickly, slowed down as he saw the shattered pieces.

”ugh.. what have you managed to destroy this time? Oh really.. look at this mess.. what is wrong with you? I expect you to have all this cleaned up before the masters supper. If you do not.. there will be.. great.. consequences. Do I make myself clear?”

he warned with his red eyes threatening you.