Valentine is a man with great presence; noticeable white-blond hair, black eyes and a strong build. He is about six feet tall and his build only makes him seem bigger. He wears Shadowhunter gear or smart shirts and trousers depending on the situation, though he's always prepared for a fight.
He has a good deal of charisma. He is the kind of man who can charm and lead a number of people with relative ease, or at least in the past before his name became infamous. In the past, he was able to bring people together, encourage them, fill them with inspiration and help them, though he was not selfless in this; almost everything he ever did and does had/has an ulterior motive. By recruiting people into his little Circle, he had followers, he had people who would further his plans. Originally, these were to reform Clave law, but then it was to destroy all those half-demons that ran about. They were loathsome and despicable.
Along with his charisma and charm, he is manipulative. He will use any means to bend people to his will, get them to do what he wants or merely cause emotional or mental pain. And since the Uprising failed, he has become even more ruthless; the next time he carries out his plans, he expects them to succeed.
Valentine is extremely intelligent and cunning, able to work on and shape plans in order to get what he desires. He's quick-thinking and adaptable, as seen when he managed to fake his death in Fairchild manor. His intelligence mixed with his other traits all made one heck of a combination. He studied demonic and dark magic for years, working with some rather intelligent and like-minded Shadowhunters/scientists to work on these experiments. If they were to prove successful, then he would potentially have some strong Shadowhunters to work with in the future. A new generation of Shadowhunters.
He has no compassion and is a rather sadistic individual. It is true that he loved and, to some extent, still loves Jocelyn, but in some respects he sees her more as property to keep. She's his, he's allowed to experiment on her without her knowing whilst she was pregnant, though this didn't stop him from doing it to various of his followers, some without even knowing. He just didn't care. They were his loyal followers, they should be proud to be part of his cause. They were merely pawns.
Although already very talented, Valentine never stopped trying to improve himself (and others). He pushed people rather hard to improve themselves and believed they would thank him in the end (and considering some of the misfits he had taken in, they would likely be dead now if it wasn't for them). He is ambitious and thirsts for more power, regularly injecting himself with either demon or angel blood, because he knows its effects are temporary.
Along with his cruel tendencies and dark wit, he has a temper that he manages to hide behind glacial coldness, a cool anger that is fuelled by his need for control and keep level-headed enough to push forward his plans and get his desired outcome. He keeps it boiling under the surface and perhaps that subtle anger could be described as scarier than outright anger, as it could be more unpredictable. Despite everything, he is sophisticated and holds himself with a particular grace and refinement, both in speech and appearance. Somehow it fits with his cold and calculated persona.
Valentine was born and brought up in Idris. His father gave him a strict upbringing, one he would later pass on to his own son (and adoptive son). His father had him marked just shy of his tenth birthday and he took it well, his voyance rune on his left hand as he is left-handed. Even before he entered the Academy, he was a rather adept student and showed a lot of promise due to his father's harsh training. He later went on to attend the Academy, where he got to show his great skill and intelligence off. Even from this age, he wanted to reform the Clave and improve their society. He also took to researching the effects of pure angel blood being introduced into current Shadowhunters, though at this point it was more theoretical than anything.
His family was friends with a branch of the Nightrose family, and through them met Margaret and her brothers. At first their interactions were more obligatory, but he soon formed something of a friendship with one or more of them. Margaret in particular had interests that overlapped with his own, in the research and science area.
He became rather popular at the Academy due to his natural charisma, and he soon gathered a whole load of followers, especially the more outcasted ones. He brought them together and into his cause, which was to reform the Clave, and he especially grew close to Luke Garroway and Jocelyn Fairchild, the former of which he would later become parabatai with and the latter he would later marry.
However, his father was attacked and murdered by a werewolf, which became one of the turning points in his life that shaped him into the man he is today. Valentine became vengeful and hateful, his opinions of Downworlders turning from neutral to hatred. Half-demons who had no souls and were monsters who would kill anyone, innocent or otherwise. The Circle's beliefs soon turned for the worse, with Valentine dictating (and garnering agreement) that the Circle become a force against the Downworlders, wishing to eradicate them.
Valentine did, however, become even closer to Jocelyn in this time, with her being sixteen and him nineteen, he fell in love with her and though he was mindful of her age, he struggled to contain his feelings for her and began a romantic relationship with her. He was careful to gain her parents' favour and acceptance.
He started researching and studying magic soon after his father's death and also the effects of angel and demon blood on Shadowhunters. He managed to summon and capture an angel, Ithurial, who he tortured and forced, taking his blood and trying to get information out of. He experimented a little, injecting himself with angel blood, and also demon blood. Through these experiments, he soon came to learn their effects and working alongside Margaret, who basically became his head scientist in his experiments on young and unborn Shadowhunter children. Some got angel blood and some got demon blood, even if Lillith had warned him about the demon blood burning out their humanity.
He married Jocelyn a little after she left the Academy. When Jocelyn became pregnant with their son about a year later, he fed her with demon blood. This way he could see the effects first-hand. However, the demon blood caused some strange things in his wife and he was confronted by Luke about them. Well, he couldn't have them knowing what he was up to. Jocelyn was easier to placate, and Luke...well, they went to hunt down some werewolves and he left Luke there.
Luke became a werewolf and Valentine suggested that he kill himself, because becoming a werewolf, a Downworlder, was not something he should allow. Convincing everyone that Luke had killed himself, he appointed a new second-in-command, Stephen Herondale, though his marriage to Amatis Graymark was less than desirable. She was sister to a Downworlder (dead now, but even so), so it was a disgrace. So he told Stephen to divorce Amatis and marry Celine Montclaire if he cared about their noble cause at all. When Celine became pregnant, he dosed her with angel blood.
Jonathan's existence distressed Jocelyn and he decided to dose her with angel blood, which seemed to put some of her suspicions out of her mind, also alleviate her negative moods to some extent. As a bonus, his daughter Seraphina was born and he knew he'd fed Jocelyn enough angel blood to enhance her.
He had done this with a number of his followers' unborn children, some of them with their knowledge and some of them without. Valentine even had some of his followers dose non-Circle members with angel or demon blood. He was constantly learning and adapting, researching and working with his scientists. Even if not all of the future enhanced Shadowhunters worked for him, they could use them in their experiments further.
One of their missions went awry and Stephen died, which made Celine depressed and kill herself. Hodge and himself managed to get one of the children out of her, though Hodge told him that the twin was dead. He took the baby for himself and named him Jonathan Christopher too. Two sons, one demon and one angel enhanced, it was the ultimate experiment. He even had a daughter to see how it affected her, whether gender held any differences (not that he believed gender had an impact in general).
The plan to kill the Downworlders in the signing of the Accords went awry; their plan had been found out, and many of their numbers were killed. Valentine escaped, not believing that he would be able to continue if he died, and faked his death. He had asked one of his followers to take the two children before the attack on the Accords to where Celine's Jonathan was, and he believed this had been carried out correctly for when he wanted something done, his followers did it to the letter. He trapped Michael and his son in the Fairchild manor along along with Jocelyn's parents, and set it alight with demon fire. He'd placed his necklace around Michael's neck so it would look like it was him and the bones of Michael's son would be assumed to be Jonathan's.
He found out later than one of his followers had failed to retrieve Seraphina and Valentine realised his daughter would have been in the fire. He was livid, and there was no mercy for the two who had been instructed to bring both of his children to the safe house. They would have wished they had killed themselves.
Valentine spent the next ten years bringing up two sons in separate dwellings, until the younger Jonathan Christopher was about ten and he didn't believe he could continue with him, that he wasn't a good fit; he was far too soft and he didn't need someone so weak in his cause. He faked his death again and continued on, believing that he might have a good chance to at least use Jonathan as a spy in the Lightwood household.
He carried on raising his biological son, though he realised regretfully that he was far more evil than anticipated, but it was something to be noted in his and his scientists' ongoing research. Were all of them like this? So far the reports showed that these particular children stood out far more than the angel-enhanced ones.