Atticus Shane is a professor at the university which Jenna attended and knew her, but he has no idea of the fact that Jenna happens to be dead. He knows "a thing or two" about the paranormal and he works quite closely with Bonnie. He is a possible love interest for Bonnie. He first appeared in the 4th episode of Season Four. He is a believer in the occult who has a history with Bonnie Bennett and her family.

Kol Mikaelson is one of the Original Vampires, and the son of Mikael and Esther. Kol is the brother of an unnamed deceased brother, Elijah, Rebekah, Finn, Henrik and half-brother to Niklaus.
Kol is a member of the Mikaelson Family.

Elijah Mikaelson is an Original Vampire, and the second son of Mikael and Esther. He has six siblings, a deceased unnamed older brother, three younger brothers (Finn, Kol, Henrik), and a younger sister named Rebekah. He also has a half-brother named Niklaus. After Mikael's death, Elijah is the oldest Original alive.
Elijah is a member of the Mikaelson Family.

Rebekah Mikaelson is a free-spirited Original Vampire. Rebekah was the lover of Stefan Salvatore back in the 1920's, daughter of Mikael and Esther, and also the only sister of an unnamed deceased brother, Elijah, Finn, Kol, and Henrik, and the only half-sister to Niklaus. After the death of Henrik, she became the youngest in the family. Rebekah has the most impeccable instincts and can tell when people are lying to her or others. This is something Klaus calls "borderline supernatural."
Rebekah is a member of the Mikaelson Family.

Niklaus Mikaelson (a.k.a. Nik or Klaus) is an Original/Hybrid, and the son of an unnamed werewolf and Esther. He has six siblings that consists of five half-brothers and one half-sister. A deceased unnamed older brother, four other half-brothers named Elijah, Finn, Kol, and Henrik. And a younger half-sister named Rebekah. Klaus is also the step-son of Mikael, with whom he had a strained relationship with.

He is first mentioned in a conversation between Rose and Stefan warning him about the Originals. Klaus is believed to be the most hated and feared of all the Originals and those who fear him are desperate for his approval. Over the centuries Klaus has become a recluse who confides in and trusts only the members of his inner circle.

For over a thousand years Klaus has been trying to a break a curse that bound him to a moonstone. He created the myth of the sun and moon curse in order to help find the moonstone and the Petrova Doppelgänger that was needed to break the actual curse. His goal was to bring out his werewolf side so he could sire his own super race.

In 1492, he finally got his chance to break his curse when he met Katerina Petrova, the final piece for the ritual. He kept her entertained until the full moon, but was unaware that she found out what he was and what he wanted from her, causing Katherine to escape from him. After Katerina turned into a vampire he assumed that her family line ended with her and that his chance to break his curse was forever gone, Klaus traveled to Bulgaria and slaughtered her entire family in revenge.

For the next 500 years, Klaus was searching for a way to break the curse without the doppelgänger and had forced generations of witches and warlocks to help him for centuries. Along his search for a way to break his curse, Klaus hunted down his family and neutralized them. Also he was searching for Katerina Petrova, who escaped him and stole his moonstone.

His love interest is Caroline. Klaus falls for her, claiming he likes her because she's beautiful, strong, full of light and "too smart to be seduced by him."

He is the main antagonist of Season 2 making his first appearance in Know Thy Enemy, in Alaric's body.
Niklaus is a member of the Mikaelson Family.

 Alexia "Lexi" Branson was a vampire and Stefan Salvatore's best friend and companion. She had known Stefan and his brother Damonfor over a century. She was killed by Damon to make others believe that she was the Mystic Falls killing vampire and was finally dead. She was 350 years old, making her birth date around 1659 and her turning year in the 1681.

In 162 Candles, it is mentioned that she visited Stefan on all of his birthdays, including once in 1987 during a Bon Jovi concert. Lexi metElena Gilbert, and gave her some relationship advice in regards to her and Stefan, saying, "When it's real you can't walk away." Elena thought of Lexi as a friend, after helping Stefan.

She came back after her death in Ghost World as a ghost to help Stefan, who got off the rails as he started feeding human blood and losing control again.

Alaric "Ric" Saltzman Saltzman was a vampire hunter and an Original Vampire. He was also a history teacher at Mystic Falls High School. He originally came to Mystic Falls to find the vampire who killed his wife, but learned that she voluntarily became a vampire and left him. He also learned that his wife had a child when she was in her teens, a daughter named Elena Gilbert, who is now his student. Alaric began a relationship with her adoptive aunt Jenna. Ironically, he was technically Elena's step-father due to his marriage to Isobel. Following Jenna's tragic death, he seemed to step into his step-father role to Elena and a father figure to her brother Jeremy. He was also Damon's best friend.

As a vampire hunter he designed several weapons to fight vampires which include vervain tranquilizers and arm vest stakes.

This character was a relative of Elena Gilbert and the Gilbert Family.

Tyler Lockwood is a main character who is a hybrid and plays for the football team at Mystic Falls High School. He was a werewolf until being successfully sired into a hybrid by Klaus.
He is the son of Richard Lockwood and Carol Lockwood, and the nephew of Mason Lockwood. He was portrayed to be arrogant, selfish and a bully. But after triggering the family curse that turned him into a werewolf, he has learned to tone his behavior down.

Before this revelation, he was referred to many times as a "dick," by both Matt Donovan and Jeremy Gilbert. He is shown to have an athletic build, and great strength as a human. He also has a short temper and becomes angry very easily. He didn't understand why he behaved the way he did, until Mason came to visit after Richard Lockwood's death.Tyler is a member of the Lockwood Family.

Katerina Petrova (Bulgarian: Катерина Петрова; English: Katherine Pierce), is a vampire and the former lover to both the Salvatore brothers, Damon and Stefan. Katerina first appeared in recurring flashbacks, depicting her physically romantic relationship with the Salvatore brothers, eventually turning them both into vampires, but was captured by the townspeople of Mystic Falls to be destroyed. To Klaus' knowledge she is a part of the Petrova Doppelgängers.

However, behind her sweet nature, Katherine revealed her deceptive side and escaped her would-be death with the help of George Lockwood (she faked her own death). 145 years later, Katherine returned to Mystic Falls and started toying with the Salvatores again, cutting off her loose ends by destroying the tomb vampires. Katherine was deeply hated for the murder and the turning of Caroline Forbes into a vampire and using a werewolf, Mason Lockwood, to retrieve the moonstone, an essential element to break The Sun and the Moon Curse. Katherine is exposed as a doppelgänger who spent her immortal life fleeing from an Original named Klaus.

And although she chose Stefan over Damon, she promised John Gilbert that she would help protect her descendant Elena Gilbert, who is the center of the Salvatore brothers hearts. She is initially portrayed as the main antagonist, but the arrival of Elijah, an Original vampire, diminishes her attitude and frightens her with the knowledge of Klaus.
Katerina Petrova is a member of the Petrova Family.

Caroline Forbes is a vampire and is the best friend with Bonnie Bennett and Elena Gilbert. Prior to Caroline's transition, she was known for her insecurities, which caused her to be excessively competitive, especially with Elena.
Throughout the series, Caroline begins dating Elena's ex-boyfriend, Matt Donovan, who encourages her to become a more caring, kind, and selfless young woman. In the Season One finale, Caroline is severely injured in a car wreck and suffers from internal bleeding.

Damon Salvatore feeds Caroline his blood to heal her. Later that night, Caroline is smothered to death with a pillow by Katherine Pierce, who found out that Damon gave her some of his blood. Caroline is shown to be very strong for her age as a new vampire. Katherine plans to use Caroline to her own advantage by eventually giving her to Klaus to kill in the sacrifice. However, Damon rescues her.

Caroline's new vampire nature adds stress to her relationship with Matt and this eventually causes them to break up, despite their love for each other. Matt's werewolf friend, Tyler Lockwood, falls for Caroline after she helps him with his first full moon. After a while, they begin a romantic relationship. Klaus also falls for her, claiming he likes her because she's beautiful, strong, full of light and "too smart to be seduced by him."
Caroline is a member of the Forbes Family.