Jack Vessalius is a nobleman from the past who ended up in house after climbing out of the Abyss. Despite being a nobleman, he seems to have a sordid past of whoring, pick pocketing, and is also a music box artisan. His clothing is historical, his manner partly wooing and partly womanizing, and he appears to be in his mid-twenties despite his own statements that he was originally older.
Jack Vessalius is a character from Pandora Hearts. His history will start with Pandora Hearts cannon before his life after the story of Pandora Hearts is explained.
Jack is the son of one of the male nobles of the Vessalius Family, a third rate noble family at the time, and a woman with whom he produced Jack in an act of adultery. Jack's father told Jack's mother that he loved her, and then abandoned her, returning to the Vessalius Household. As Jack was growing up, his mother gave him a keepsake with the Vessalius crest on it while telling him that he looked so much like his father; the man she loved.
People often were crude to Jack, calling him disgusting for being born out of wedlock. Jack's mother eventually went crazy with her obsession and loneliness. She is shown beating Jack, questioning him as to why his father never came back for her, as she'd been waiting all those years just for him. This made Jack hate his parents and ran away for an unknown amount of time.
Jack was dirty, cold, and wrapped in an old blanket in the streets when he was approached by a girl about his age, with black hair and red eyes. She introduced herself as Lacie, while Jack inwardly wondered just who she was. Soon the girl sat down and began explaining to Jack that she had run away from home because someone named Oswald got into a disagreement with her, so she wasn't going to return home until he apologized. Jack was still confused as to why she was telling him this, saying that he didn't really care. Lacie got annoyed with him, informing him he should have several questions especially why she was wearing such a light dress during such cold weather. Lacie explained that it was so cold that she could die, and jumped into Jack's blanket with him to stay warm. Jack asked harshly what was wrong with her, and she asked if he was finally taking an interest in her because he'd asked her a question.
After Jack had been fed and clothed by stolen goods from Lacie, she began cutting his hair with the scissors she'd also stolen. Having noticed a necklace tied around Jack's wrist that had the Vessalius Family Crest on it, Lacie asked if he was related to them. Jack then proceeded to tell Lacie about his parents and how he hated everyone because of them, but he said that it didn't matter because he'd already lost everything. Lacie slashed Jack in the ear with the scissors, saying that he looked cute when he was in pain. She told him that he hadn't lost everything... he'd only lost his will to live.
The rest of the encounter ended with Lacie defending Jack before giving her one of his earrings after learning that Oswald had apologized and that Jack should find her next time and not to forget the name "Baskerville".
Glen then told him that if he was to be tortured and murdered, the other Baskervilles wouldn't say a word, as he was the Leader. Jack, asking if that was his intention, asked that before killing him 'at least let me see Lacie once more'.
Glen then received more on Jack, ignoring for the moment his threat against his life, as he never knew anything about a Jack being in the Vessalius house. When Jack looked quizically at the attendent who understood his past and present information, Glen removed the hood of the Baskerville that was hiding behind him. He introduced him as Oswald, his personal attendant.
Jack nervously asked if he knew Oswald from somewhere, as he recognized him. Oswald said no, as it's his job to montior the people around the mansion and this is the very first time meeting him face-to face. Glen said that it's surprising to seeing Oswald so interested in other people. Owald said yes, but said that he couldn't help but notice Jack. He then said that he couldn't help notice how Jack was making people unhappy. Oswald went on to say that Jack was like clear water to the point where there are no fish meaning that there are few people within Jack's circle of friends. Lacie then came and grabbed Jack away from them at that point after finally remembering who Jack was.
Soon after this, Jack was given a map of the secret passages of the Baskerville estate by Glen and was told to come back and visit. This was to be one of the last times he would ever see Lacie Baskerville again.
Friendship with Glen
After his reunion with Lacie, Jack became best friends with Oswald. Oswald, at the time, was not yet Glen but that would change soon after. Together the two of them crafted a musical pocketwatch, which was meant to be a present for Lacie. The song the watch played was the song that Lacie had given words to, but Oswald had composed.
Not long after this, Lacie was sacrificed to the Abyss by her brother Oswald, when he became the new Glen, for 'having the red eyes of a child of misfortune, and threatening the peace of the Abyss.' This caused Jack to fall into a deep trance-like depression before suddenly being vistied by Revis Baskerville, the previous Glen. Jack was 'enlisted' by Revis, who revealed that he had fathered two children with Lacie just before she was cast into the Abyss, and believed that because of his new accursed state he would deteriorate before he could see the end results. He then gave Jack permission to use Alice to gain his wish; which without question was the return of Lacie.
Revis explained to Jack that his reason for fathering children with Lacie was an experiment to create a vessel for the core of the Abyss. Revis hadn't originally realized that his experiment was a success but not only that but had an unexpected result: at the time Lacie was cast into the Abyss, she was carrying twins.
One girl was sent back and was placed in the very tower that Lacie had lived in, but despite looking very similar to a young Lacie, the girl's name was Alice, not Lacie. She revealed to Jack one day that she shared her body with another Alice. The other Alice wasn't social and only seemed to care about Jack.
At one point Jack found Glen in the woods, sleeping with a bird on his head. Glen asked him what he was doing as Jack crept closer, and Jack observed that Glen had been awake. Jack smiles and says that he wishes the other men could see this, and explains to Oswald that he is relieved that he is just like everyone else. Glen denies it instantly, saying that Baskervilles cannot die as easily as Jack and the others can, and explained to Jack that he transfers his soul to a new body every 100 years. Glen also explains that Celia's chain, Humpty Dumpty, was his last body and that Humpty Dumpty would be able to locate his soul if it was ever lost before anyone else. Jack calls this attraction "kind of romantic", and catches Glen's interest. Glen then says that if he was ever lost for 100 years, Humpty Dumpty would be the one to find him.
Jack snuck up on Lottie while she was spying on Glen Baskerville in their first encounter, at which she suddenly pulled a dagger on him. Glen noticed and told Jack to stop messing with Charlotte, and upon hearing her name, Jack started calling her Lotti, a name which she kept for 100 years.
Jack was known to often use secret passageways in the Baskerville mansion in order to come see Glen. On one occasion Charlotte found him and pounced, yanking on his braid while holding him down with her foot. She heatedly asked what he was doing there; as she knew the doors were all guarded and watched, but still he found his way in day after day. When he explained how he got in, she released him and sat on him, asking him what his relationship was with her master. He looked up at her, wondering why she wouldn't just ask Glen directly. She confessed that she couldn't approach him, and Jack told her simply that he was his friend. Lotti found it suspicious, since her master liked to be alone, and in all occasions was not interested in loud men like Jack.
One day, Jack and Glen found the tower in the middle of the woods not far from the Baskerville mansion. There Jack finds Alice, although he had already been shown this tower and Alice by Revis, whom he befriends (because of how much she looked like Lacie, and because she had been confined in the same place). Jack then came to see Alice most days after their encounter to play with her, even promising to take her to the Vessalius' rose garden one day.
Though Alice looked much like Lacie, and he befriended her, there was another personality that inhabited her body every now and then. This personality was The Will of the Abyss. Jack could tell she was different from Alice because of her love of light clothing and because Cheshire loved her, whereas when Alice was in her own body, Cheshire (Alice's cat) hated her.
This was when Alice explained to Jack about being twins, and that the Will of the Abyss was also named Alice. When the explanation of this was through, Jack understood more about Revis' experiment.
More information is here for now: http://pandorahearts.wikia.com/wiki/Jack_Vessalius