Jack has a somewhat normal appearance, save for minor details that make him seem like someone belonging in an asylum rather than on the street. Most obvious is his unusual, naturally lavender hair, wavy with few particularly curly, darker purple streaks, a trait he inherited from his parents. His eyes are also of a purple-ish hue, though they have less color than his hair, and appear more silver than anything else. They are rimmed with dark, black-ish bags, as though he doesn't get enough sleep or deals with a lot of stress, both being factors in this tired, sickly appearance of his. Jack's skin has an almost unhealthy pale complexion, without any blemishes or marks, like that of a porcelain doll. As far as body type goes, Jack is a bit too skinny for his towering height of 6'1". He weighs an average of about 120 pounds, giving him a lean and wiry appearance and causing his younger brother to fret over him, for he doesn't ever eat nearly enough.

Clothing-wise, Jack is pretty well off. He raises plenty of money as a surgeon, and as a result is able to get his hands on some expensive-looking clothing specially tailored for him alone. It usually has a Victorian air about it, with slight steampunk elements thrown in, for he adores the casual elegance of it. Typically his clothing consists of simple vests over dress shirts that tend to vary in color, tucked into darker colored pants which are held up by leather belts of different sizes and shapes, depending on the style he's going for that particular day. Due to his hobby, Jack often has new clothes made, for blood doesn't wash out very quickly or easily, and he doesn't want Luca to ever discover what he does when he's away from home.

Jack is a very... unstable individual. His personality can vary widely from innocent and excited to bloodthirsty. This is not something he's able to control, and on occasions there are moments where he himself is unaware of these shifts, either choosing not to remember or forgetting them entirely. However, there is one factor in his life that is able to take moderate control over his actions, and that is is younger brother. Luca acts as both Jack's brakes and gas pedal, urging him to stop when he gets out of hand yet also causing his dangerous changes in personality to skyrocket if and when he gets into trouble. Essentially, everything Jack does is driven by Luca, in an unhealthy and mentally taxing relationship on both sides. 

One important activity, or hobby one could put it, that Jack indulges in is murder. He'll leave the house, sometimes for days at a time, engaging in the slaughter of numerous people, typically beautiful women, and the "recreation" of their lifeless bodies. His victims have been found in various states, torn to shreds, posed in mannequin-esque sculptures, and cut into numerous pieces and scattered across the scene. These methods earned him the nickname, "Jack the Ripper", though other than his name his true identity still remains unknown. In whatever fashion he leaves them in, Jack's victims are always stripped of their clothing and whatever other valuables they were killed in, presumably before their deaths, for no bloodied scraps of cloth are ever found on the scene. Unbeknownst to both the rest of the world and his brother, Jack brings these clothes he gets home as presents, or trophies, for Luca, lying and saying that he bought them himself which, in one way or another, he sort of did.

As for fears, Jack has very few, though one of the most prominent is the ocean, and the creatures that reside within it. He's entirely put off by the sea, let alone the "monsters" it births, and won't go anywhere near it. This is one of the factors that kept him from consuming an actual aquatic creature to shift into, instead deciding on an animal able to go both in the water and out.

Jack is a skinwalker, of the more morbid and disturbing variety. Essentially, he is able to transform into a maximum of three animals, divided into the categories land, sea, and air. He is able to choose his own animals, by simply killing, consuming, and absorbing them into himself.

The land animal Jack chose was an east Siberian brown bear, smaller than its Eurasian counterparts but nonetheless ferocious. It has a silvery-brown pelt, thick to handle the cold climates it lives in, and acts as an apex predator in the environment in which it resides. Jack's sea creature is, well, not necessarily a sea creature at all, for reason's he's far too embarrassed to reveal (see personality). Instead of choosing a true aquatic animal, he decided instead on a creature that resides both on water and land, cheating the system in a way. He chose a Nile Crocodile, ferocious, large, with a bite more powerful than nearly any other creature like it. Its leathery hide is dark, almost black, in color, and hard to the point that its difficult to even make a dent in it. And finally, his avian creature. After numerous failed attempts at hunting eagles, hawks, and falcons, Jack finally turned to owls, and managed to gather one that was not necessarily the scariest of them all, but looked about as regal and intimidating as an owl could get. He chose a northern hawk owl, with dappled, deep grey feathers and piercing yellow eyes, a low brow framing them in a manner that made the creature look like it was glaring at you. 

Jack chose an entirely predatory group of animals for a very simple reason: to protect his brother, Luca, who didn't exactly decide on the most intimidating creatures in the world. He was worried his younger sibling would end up getting hurt while in one of these animal forms, and wanted to have a way to properly protect him if he needed to.

Jack was born to a family of aristocrats, and one with a rather high social standing at that. Money poured in without his parents even lifting so much as a finger, running a business that held some amount of influence in nearly every district of the city. It was this very business that Jack was set to, one day, inherit and administrate, taught daily by his father and various tutors on how to act properly in public, how to hold formal ceremonies and balls, and other, more academic subjects such as mathematics, language, and science. Jack excelled in all of his classes, to the point that he was at nearly college-level courses when he was a mere 16 years of age.

However, this intelligence of his acted as more of a deterrent to daily life than anything else. He grew bored of studying, bored of music lessons and learning how to properly waltz. His existence as an aristocrat, so high above everyone else within the city, made everything so dull. It was then that he began to grow infatuated with the human body. It was so fragile, yet resilient. Cutting it open was the easiest thing in the world if you weren't scared, and yet depending on where you cut, your patient could go days without being sewn back up. The elegance of it all excited Jack; he wanted to know more, experience more, about the human body and all of its beautiful flaws. And so, he did.

Gaining access to the bodies proved simple; the slums were the perfect place to start. He donned one of his less fashionable cloaks and boarded an airship to the grimy, criminal-infested district, taking care not to attract too much attention while he was there. Beneath his cloak he had hidden various tools, serums, and bandages. He seemed almost suited up and ready for a surgery, rather than a murder. His very first victim was a young woman, surprisingly well off for someone tucked away in the slums. Dirty, yes, but with soft skin and beautiful curves. She was like a gorgeous piece of art just ready to be sliced open. What happened after he'd caught her, however, was lost to the ever-shifting tides of his memory. All he recalls is the feeling of euphoria and utter excitement he felt as his blades tore through her milky white skin, and the delightfully off-tune melody of her screams. 

It was during another one of these little trips, years later, after he'd received great recognition for his accomplishments in the medical field, that Jack met the boy who would later become known to him as "brother". It was a dark, silent night, eerily so. He had been prowling the residential district, searching for an early riser or someone who'd spent far too much time in the Red Light district to find their way home, when he heard the cracked sobs of a young boy. In the faint light of the moon, he turned his head to see a child, golden blonde hair shining, blue eyes puffy and cheeks stained with tears. Blood was trailing down his leg and staining the cobblestone path beneath his feet. He was beaten, broken. He would die soon, painfully, if he wasn't treated. 

For some reason, even after countless victims and merciless torturing in order to study and surpass the limits of the human body, Jack was hesitant about taking the boy's life. Something about the pitiful way the kid held himself, the way he cowered away from the open road, hiding as best he could in the shadows... He just couldn't bring himself to kill him. So instead, Jack did something he'd never thought was possible—he saved him. Using the makeshift antiseptics and bandages he'd brought along with him, Jack bound the boy's wounds, treated his cuts and bruises, cleaned away the blood covering his skin. During this process, Jack came to know the child as Luca, and with great malice he learned that Luca's father was the one responsible for each and every one of the injuries that littered his body.

Jack brought the boy to his own home, lending him his bed for he never slept in it anyway and making sure to hide away any particularly shocking items. Hours passed, some of which Jack spent absentmindedly looking over the kid he'd taken in. He was the very embodiment of innocence, wholly surrounded by the sins of a murderer, and not once did Jack even think of cutting him up.

When the sun broke over the horizon the next day, Jack was already gone, and little did he know Luca had woken up and was set to arrive exactly where he himself had gone out of his way to go. Nonetheless he worked quickly. He tore through the boy's home, far more aggressive than he usually was, searching in a rage for his father. He fully intended to take the man's life, and make him suffer just as much as Luca had the night before. When he did find him, Jack very nearly lost all composure. He lashed out, quick and skilled after years of hunting down other people. It didn't take long before Luca's father was sprawled out on the ground, shortly followed by his mother, gasping harshly for air as their own blood seeped into the carpet. 

Luca arrived shortly after Jack had finished, breathing heavily and gripping the blood-stained, shattered half of a wine bottle in one hand. It was soon dropped, and the murderer's arms were around the kid, hugging him tightly in a sorry effort to comfort him. It was then that Jack swore to himself that he would keep Luca safe. He wouldn't let anyone hurt him, wouldn't allow a single person to even lay their hands on him, else he would do to them exactly what he'd done to the boy's parents.