A perpetually-cowled man of the shadows who offers quality medical services to all manner of mortal and immortal creatures. He asks no questions each time treatment is requested, but the payment? Well. That varies every time.
A complete enigma in terms of personality, Doctor Shady has gotten so good at concealing his emotions over the years that most of his clients can't tell what he's feeling about them, what he's thinking, or what he plans to do next. In fact, the only thing they can trust is his reputation - Doctor Shady will aid anyone, good or evil, mortal or immortal, angel or demon, etc, etc, as long as you agree to his price. People who have met him and used his services describe him as quiet, mysterious and sometimes cynical. He often makes darkly humorous quips while operating, simply to put a scare into the patient he's operating on, though he has never compromised anyone's safety.
Doctor Shady, being a man of medicine, walks around with a briefcase full of highly-potent chemical cocktails and first-aid equipment, and keeps his operating tools (most of them razor-sharp and doubling as hidden weapons) concealed under his labcoat, in neat little steel cases, all of them sanitized before being stashed. He has his own underground clinic, but in case he needs to perform emergency medical procedures, he usually relies on his innate skill and the tools he happens to carry around.
It is unknown, exactly, where Doctor Shady got his training, if he's even a licensed doctor, who he trained under, which school he attended, or what inspired him to be a neutral doctor who does not judge who he serves. He fits snugly into the multiverse, and, depending on the setting or characters he is exposed to, his story promptly changes accordingly. For example, if in a Medieval setting, he simply states that he was never educated at a college, but took up his trade from a wandering medicine-man, apprenticing under this mentor-figure before travelling the world to learn the medicinal remedies of different cultures before getting where he was today. If in a Victorian/Elizabethan or Steampunk setting, his background is that of a disgraced student at a prestigious university who was expelled for unholy, disgusting eldritch practices that were not acceptable in gentle society. He was cast out, and had his reputation crucified, and now only the desperate or the nocturnal come for his aid. For every setting, he has a different background, but in every setting his background has a few similarities: He is either unlicensed, or licensed but disgraced, hence his underground status and reliance on the more criminal sort as his customers. He tends to anyone who comes to him, without questions asked, but with an odd price, which varies each time and with each customer. A mass murderer seeking his aid, for example, would be asked to apologize to the families of his very first victim. A decorated war hero would be asked to travel to the country where he fought and meditate on the streets. Doctor Shady does not check to see whether his patients follow his conditions - he merely treats them, states his price, and bids them farewell.