Sebastian is an old vampire who has been alive for over six hundred years. He describes having lived in the golden ages of vampirism; times when vampires were not afraid to feed on humans. He states that men trembled at the mention of his name.
At some point around 1585–1590, he feed on and terrorized the settlers of Roanoke — he fed on so many humans that it was no longer for hunger and it was for mere sport, so much so that cobblestones ran red with blood. In Roanoke, there was a powerful witch, named Cassandra, who came to be his great love. She gave him a token to protect him from the colony leadership as they had asked Cassandra to find the monster that was that was terrorizing them. Cassandra however did love him and summoned something even worse. She summoned a croatoan - something that would ferret out the lies that the Puritan hypocrites were concealing from the rest of the village. Something to keep the leadership from finding him. The croatoan however went crazy. When he found out what Cassandra was plotting, he tried to stop her because she was keeping his secret and feared that she'd become a target. To further keep Sebastian safe, she desiccated him. In that state, he watched the croatoan tear her limb from limb before she could dispel it. Unable to help her as she died.
He remained imprisoned and desiccated in the coffin for the next four hundred eighty-three years.
Throughout Legacies Series
In This Year Will Be Different, as Lizzie is waiting at the Old Mill for MG to arrive, she notices Sebastian standing in the shadows. She assumes he must be new, but questions who he is given that she knows all of the incoming students. He asks her where he is, clearly confused. She tells him they're at the Old Mill, explaining that they are at the Salvatore Boarding School for the Young & Gifted. This surprises him as he didn't know it was a school. She attempts to help him when he becomes unsteady, and he warns her to stay away from him.
She later uses a locator spell to track him, which prompts him to realize that she is a witch. He warns her to stop trying to locate him as he is not good for her, but she later tells MG that she has fallen for him, despite his warnings.
In You Remind Me of Someone I Used to Know, Sebastian arrives to watch Lizzie during the Annual Charity Football Game between Mystic Falls High and the Salvatore School. Lizzie notices him and when he leaves, she follows him to the basement of the school. Sebastian tells her that he had to see her again, but can't be with her. Lizzie asks what he is, and he explains that he is a vampire, much to Lizzie's relief. He is confused by her reaction and explains that he has been in a romantic situation like this before. With that, the two kiss, which is witnessed by MG from afar. He is unable to see Sebastian, and it appears as though Lizzie is kissing the air.
In Since When Do You Speak Japanese?, Sebastian and Lizzie go on a date by the lake behind the Salvatore School. MG, in his efforts to prove that Sebastian is a figment of Lizzie's imagination, borrows recording equipment from Wade. He uses this to record the date, and it proves that Sebastian can only be seen by Lizzie — she is disgusted by MG's treatment of her, but is also heartbroken, believing that she has imagined Sebastian. At the end of the day, Sebastian appears to MG, questioning what he said to Lizzie. Wade questions who MG is talking to, and Sebastian further reveals that MG is the only one who can see him.
In Screw Endgame, Sebastian continues to communicate with MG, as he begs for his help. Sebastian explains to MG, who relays the information to Kaleb, that he has been desiccated for centuries somewhere under the Salvatore School, however due to the recent drop of blood from the fountain, he was able to gather enough strength to reach out mentally. After MG questions why nobody else can see him, Sebastian reveals that he is currently too weak to reach out to anyone other than those of fragile mind, which explains how he was able to reach out to Lizzie.
MG and Kaleb find his body, but are both unsure of what to do with it, as they have little information on why he was desiccated in the first place. They decide to consult Alaric, who tells the two that it is best to leave him desiccated, as they have no idea what they could be unleashing upon the Earth if they choose to wake him. With this, Kaleb feeds Sebastian small amounts of blood, just enough to increase his strength to the point where he can contact Kaleb mentally. Kaleb questions why he was desiccated, and he reveals that it was due to his violent nature as a vampire; behavior similar to that of a ripper. With this, Kaleb tells Sebastian that he will burn his body after the dance.
Unbeknownst to MG and Kaleb, Sebastian has increased his strength enough to reach out to Wade, and the two have a brief conversation before Wade presumably wakes Sebastian up. Sebastian gives MG one final glaring look before leaving the Salvatore School behind.
In That's Nothing I Had to Remember, Sebastian is awake having fed on Wade. Kaleb, Kym and MG set up a trap to catch Sebastian, offering Kym as bait. When he tries to attack Kym, they trap him and snap his neck. They tie him up in Alaric's office at Mystic Falls High School, out of Lizzie's way, as she is still under the impression that Sebastian is fiction.
When the croatoan attacks, Sebastian is able to offer pivotal information about it, including what is is after — secrets. He is fuzzy on the details initially, though, until Josie casts a spell that returns everyone's memories. He remembers details about his former lover, Cassandra, including that she summoned the croatoan to find the monster terrorizing the Roanoke colony — he later realizes that she was aware he was the monster, therefore gave him a necklace to protect him. He offers the necklace to MG as a way to kill the croatoan, and is left heartbroken after remembering that Cassandra desiccated him to protect him, but forcing him to watch her be ripped apart.
When Lizzie is discussing Landon's choice with Josie, Sebastian appears, and it is apparent that everyone can see him. MG tells Sebastian that he has something too tell her.
In This Christmas Was Surprisingly Violent, Sebastian joins Lizzie on the road trip to return Landon to the Salvatore School. On the trip, it is revealed that Lizzie had spelled a daylight amulet for Sebastian, but brought him along on the trip only because he keeps her sane. He questions if the two can stop for something to eat, but Lizzie tells him he should've eaten before they left. When Lizzie tells Sebastian she saw a deer he could eat, he gets out of the car and she leaves him by the roadside.
He later catches up with her outside of Rafael's father, Walt's house. The two joke, and Sebastian takes off his shirt as he is attempting to change a tire. Lizzie tells him to put it back on, however it is no use and she ends up kissing him. The two have sex in the car, and afterwards, Sebastian tells Lizzie that he would like to remain at the Salvatore School as it is the only thing he has left.
In I Couldn't Have Done This Without You, Sebastian has began his integration to life at the Salvatore Boarding School for the Young & Gifted. Alaric, however, feels that Sebastian is dangerous, and should be assimilated into student life the same way Landon was — through a series of assessments. As the only one who cannot be killed, Alaric tasks Landon with carrying out the assessments.
Sebastian takes part in assessments relating to each of the factions of the school. He interacts with the werewolves during a game of dodgeball, and he becomes visibly angry when Jed manages to hit him with a ball to the face. He manages to calm himself, however, and is invited to join the future games. His next assessment is to see his interactions with the current vampire population, given his advanced age of over five hundred. MG sees this as an opportunity to oust Sebastian, and with the help of Alyssa Chang, he tries to tempt Sebastian with the sight of blood. MG is the only one truly affected by the blood, however, and Sebastian uses his advanced age and strength to restrain MG, calming him. He warns Landon of MG's attempts, referring to him as a Ripper.
Sebastian's final, and hardest test, is his interaction with the witches. Sebastian agrees to allow Alyssa use a crystal ball on him that reveals his true feeling. She begins pushing Sebastian and it becomes clear that he fears modern day society, but also that Lizzie will find out about his history. With this, he warns Alyssa to stop, but she continues pushing, causing him to lash out at Landon and the witches to simultaneously attack him. He flees following this, but Landon still tells Alaric that he passed all of the assessments and should be given a chance at the school. Alaric, however, is less than certain as he reads a chapter in a book titled "Sebastian the Merciless".
Sebastian, angry at the events of the day, attacks a jogger running through the woods around the school. He is stopped by Alaric, who shoots him with an arrow and warns him that he has had a locator spell on him since the minute he stepped onto campus. Alaric tells Sebastian that he is willing to accommodate him at the school as long as he follows his rules; Sebastian remarks that he is done following rules, however. Sebastian warns Alaric that Lizzie will not be safe at the school as long as he is alive, and the only way for her to be safe is if he is killed.
Alaric is later seen cleaning blood from his arrow in his office, however it is not made clear if he killed Sebastian or not. When Lizzie asks about Sebastian's whereabouts, he tells her that he chose to leave the school, and Lizzie breaks down, remarking that it is the best thing for her.
So far, Sebastian is shown to be seductive and vile. However, after regaining his memories of his lover's sacrifice in order to keep him safe, he has also shown to have a much softer side.
Physically, Sebastian is a handsome and brooding man with longer than average, parted brown hair. He has piercing blue eyes and strongly defined features that instantly attract Lizzie Saltzman, despite not knowing him. His attire is a little dated, given he is over six hundred years old, but he still manages to present himself cleanly.
Powers and Abilities
Sebastian possesses all the standard powers and abilities of a non-original vampire.
Sebastian has the typical weaknesses of a non-original vampire.
- This Year Will Be Different
- You Remind Me of Someone I Used to Know
- Since When Do You Speak Japanese?
- Screw Endgame
- That's Nothing I Had to Remember
- It Will All Be Painfully Clear Soon Enough (Mentioned)
- This Christmas Was Surprisingly Violent
- I Couldn't Have Done This Without You
- This is Why We Don't Entrust Plans to Muppet Babies
- Sebastian is from the Latin for "venerable" or "revered". 
- Based on the character slides, it was initially believed that he had connections with the Salvatore namesake, having known of Stefan and Damon Salvatore.
- It appears that this storyline was retconned, as Sebastian has no idea who either of the Salvatore brothers are; nor is he 600 years old as the slide implies.
- He is possibly a love interest of Lizzie Saltzman.