Undertaker has long grey hair with a few braids throughout, which is worn so as to hide his eyes. His eyes are apparently quite nice. He has a noticeable scar across his face, neck, and left pinky finger, although how he acquired them is unknown, and has long, black fingernails. He wears all black, including an incredibly long, black top hat, and he wears a long, grey scarf across his chest, with it knotted by his hips.
Undertaker enjoys frightening people, dressing intentionally creepy to cause a reaction from them. He has shown that he likes being a caretaker for the dead and informant to the Phantomhive family since he has been since before Ciel's father's time. He also requires his payment not by "the queen's money" but by having someone amuse him.
He also shows to be flirtatous when Yuki and Juliet come for information he always grops them from behind as a greeting. He loves kissing Yuki often requesting for a "taste" in exchange for information. He seems to love to torment Juliet as when he lifts her skirt and tries to touch and kiss her knowing how much she hates him. He claims he does this because her reactions are "adorable".
He is known to call the dead his "guest" and takes the organs of his "guests" for research. He is known to eat dog-bone shaped biscuits and tea out of a beaker.