Elijah Mikaelson

Elijah was first introduced when two vampires named Rose and Trevor called a person on Elijah's inner circle in the hope that he would come to meet them and pardon them because they were tired of constantly running from the Originals. They held Elena captive in the hope of using her as a bargaining chip. Initially skeptical of their claim of having the Petrova doppelgänger, by testing whether Elena was human, he proceeded to smell her neck. Surprised, he confirmed that Elena was indeed a human and alive. He forgave Rose because she helped Trevor out of loyalty to him which he respected, but he executed Trevor by decapitation for his betrayal of having helped the second Petrova doppelgänger, Katerina Petrova, escape.

As they were leaving the house that Rose and Trevor were hiding out in, the Salvatore brothers came to rescue Elena. They shot Elijah in the hand with a wooden stake, Elena then came out and threw a vervain grenade which exploded and burnt his face; however, he soon healed. Stefan shot multiple stakes at him and eventually tackled him to floor. When Elijah got the upper hand and was about to kill Stefan, Damon then staked him with a broken coat rack, pinning him to the wall; however, some time later, he came to back to life and pulled the stake out of him.

Elijah saves Elena and Damon from Klaus' minions.When Rose and Damon went to see a vampire named Slater looking for information about the curse, Elijah appeared and gave a guy a 100 dollar bill in exchange for some coins. He listened to the conversation for a while before throwing some coins at the web-Café's special UV protected glass. It shattered, which sent the vampires inside running for cover. Later that night, he compelled Slater to call Rose (who was with Damon) and tell her that they can stop the sacrifice by dispelling the moonstone. Elijah then further compelled Slater to stake himself.

Mikael

"Nobody cares about you anymore, boy. What do you have? Other than those whose loyalty you forced. No one. No one." -Mikael to Klaus in Homecoming episode.

Mikael was an Original Vampire who was once a wealthy landowner in a village in Eastern Europe. He is the patriarch of the Mikaelson family. He was the father of Elijah, Finn, Kol, Rebekah and Henrik and the step-father of Niklaus. He was in his late 40's to early 50's, and was seen to be strong, controlling, domineering, strict, and authoritarian in nature. After moving to the New World, his wife bore six children and his family was quite close, though he and Klaus didn't get along well at all, due to the fact that Klaus was not his son and was from a Werewolf Bloodline. His wife had been unfaithful many years before and when he found out about her affair, he hunted down and killed Klaus's father and his entire family, not realizing that he was igniting a war between species that rages to this day, the war between the vampires and the werewolves. Mikael was the one who asked Esther (wife) to turn the family into vampires. 

In Homecoming, Mikael helped Elena and the Salvatore Brothers to lure Klaus to him so he could kill him for good. To do this, Klaus needed to think that Mikael was dead, so Elena temporarily daggered him and later revived him. When Mikael returned to life, Rebekah was there to talk with him. He said that his intent was never to kill her, only Klaus as revenge for killing her mother. Rebekah told him that she knew what Klaus had done, but blamed Mikael for making Klaus this way, saying that it was not Klaus who destroyed their family, but Mikael when he turned them into vampires. 

Mikael meets with Klaus for the first time in 1000 years. Later, Mikael showed Damon the White Oak Stake, the only weapon that could permanently kill an Original. Damon asked him why he feeds on vampires. His reply was:"I had a hand in creating vampires but the blood lust was never my intention. Over the centuries, I've learned to feed from the predator, not the innocent."

Mikael kills Elena in front of Klaus. When Stefan came in, he fed on him and went with Damon to the Lockwood Mansion to proceed with the plan. At the mansion, Mikael found himself surrounded by hybrids. Klaus says that his hybrids will kill Mikael. Mikael replied that they cannot kill him, to which Klaus says "But it will make a hell of a party game". When Klaus came to the door, he tried to get Klaus to come out of the house to fight him, to no avail. Mikael dies.
Mikael bursting into flames after getting staked with the White Oak Stake. 

Damon Salvatore

 “Let me be clear about something. If it comes down to you and the witch again, I will gladly let Bonnie die. I will always choose you." - Damon to Elena.

Damon Salvatore is Stefan's elder brother. He was born in 1840 and lived in the colonial town of Mystic Falls with his brother Stefan and his father, Giuseppe Salvatore. He became a vampire in 1864. At the time of his return to Mystic Falls, Damon and Stefan hadn't seen each other in fifteen years due to their bitter, violent relationship. 

Damon is some sort of a bad guy. He looks bad, he's acting bad and make people getting pissed off of him but deep down in his heart, he's a very emotional guy and has a great sense of sympathy towards his dear one. He will do anything to save them. He's even more emotional than his brother Stefan and willing to fight and sacrifice himself for the sake of his love. Later, after Katherine, Damon and his brother Stefan both fall in love with Katherine's doppelganger, Elena Gilbert. 

Damon's sole purpose in coming back to Mystic Falls was to free Katherine Pierce, the vampire who turned him and the woman he deeply loved. After realizing that Katherine never loved him, his love for her fades as his friendship with Elena, Katherine's descendant and doppelganger, grows. Due to her impact on him and the strengthening relationship with his brother, they begin working together and protect Elena, her friends and family. He currently lives with his brother, ex-girlfriend Elena (when she isn't away at college), and her brother Jeremy Gilbert in the Salvatore Boarding House.

Stefan Salvatore

"For over centuries I have lived in secret, hiding in the shadows, alone in the dark. I'm a vampire and this is my story." Stefan was born on Veritas Estate in Mystic Falls, Virginia. He is the second son of Giuseppe Salvatore. During his human years, his older brother Damon was his best friend and companion until they both in love with the same woman, Katherine Pierce, who turned both Salvatore brothers into vampires.

Stefan was the first one who met Katherine, right after his brother Damon. She openly flirted with both brothers. It was Stefan who wins the heart of Katherine and since then the bond between Stefan and his brother Damon is on the rock. Katherine chose Stefan to escort her to the Founder's Ball. 

"I've never met a woman quite like you. 

I look at you and I see an angel. 

I touch your skin my whole body ignites, 

I kiss your lips and I know that I've fallen in love." 

-Stefan to Katherine.

Right after Stefan confessed his love to Katherine, though she was surprised, she was clearly pleased. Stefan and Katherine were spending a passionate night together when she suddenly bit Stefan. The next morning, Stefan awoke with a bloody wound on his neck, and the previous night slowly returned to him. He was clearly frightened of her, saying that her face resembled that of a demon. To calm him down, Katherine compelled him to not be afraid of her. 

Stefan was first seen as a mysterious, handsome and new high school student at Mystic Falls High School. He was born and raised in the town of Mystic Falls and had just moved back to town, where he lives with his nephew Zach in the Salvatore Boarding House (he lived in Salvatore Estate). Zach refers to him as "Uncle Stefan", even though Stefan looks significantly much younger. When Stefan first arrives at the high school, all the girls are irresistibly attracted him and want to gain his attention.

It is at the high school that Stefan inevitably and fatefully meets Elena Gilbert, who bears an unusual, and striking uncanny physical resemblance to Stefan's past love from 1864, Katherine Pierce. Upon meeting each other, Stefan and Elena are instantly, undeniably drawn to each other and the two instantly connect. 

Katherine Pierce

Katerina Petrova (Bulgarian: Катерина Петрова), better known as Katherine Pierce, is a witch of the Traveller subculture, the third doppelgänger of Amara, a former vampire, a major antagonist and one of the main characters of The Vampire Diaries. She was the main antagonist of Season One (through John Gilbert's and Isobel's actions, as both were working for her), and one of the antagonists of Season Two. She was also a recurring character in the Third and Fourth seasons. Finally, she has a main role in Season Five.

After giving birth to a baby girl out of wedlock around age 17, and being forced to give the baby up for adoption, she was disowned. She was exiled to England, where she quickly assimilated into her new culture and met two nobleman brothers, Niklaus and Elijah Mikaelson. At first, she was attracted to the two brothers. However, she later learned that she was a Petrova Doppelgänger, and that Klaus was planning on using her as a sacrifice in order to break the curse that bound his werewolf side. She sabotaged his plan by running away with the moonstone, which bound the curse, and then tricked Rose into feeding her her blood so she could turn herself into a vampire. Because Katherine was no longer human, she was no longer a candidate to break the curse. Klaus was so infuriated with Katherine's sabotage, that she was forced to live on the run for over 500 years as he hunted her down.

Her activities during her first centuries as a vampire are unknown, but at some point between the 15th and 19th centuries, she took on the alias Katherine Pierce (which is an anglicized version of her birth name), and eventually met and befriended Pearl, Anna, and Emily Bennett. In the late 19th century, she traveled to Mystic Falls, where she met Stefan and Damon Salvatore while they hosted her at the Salvatore Estate. She later fell in love with both brothers, and subsequently turned them both into vampires. When the Town Council found out the identities of the vampires in town, she faked her death and escaped being sealed in the tomb, with the aid of George Lockwood, who helped her in exchange for the moonstone.

Niklaus Mikaelson

Niklaus Mikaelson a.k.a Klaus. What so special about his character is that he's considered among the most powerful mystical immortal. He's not just a vampire, or a werewolf, he is an Original and a Hybrid. The Original Vampire or also known as "The Originals" are the world first vampires from which all current vampires descend from and most dangerous. He is different from the rest of his siblings due to her mother's affair with a man from the neighboring village, whose inhabitants were known to be werewolves. Klaus and the rest of his family turned into a vampire with "mortality spell" cast by their mother, Esther who is a witch as a form of protection when his brother Hendrik got killed by a werewolf in their village during the period of a full moon. 

Vampirism is actually a form of protection. No one knows that Niklaus is not the biological son of their father, Mikael not until when his mother turned their family that night, Klaus' blood-lust became particularly strong and he transitioned into a hybrid after his first kill, due to his werewolf gene. However, Esther later bound his werewolf powers to the moonstone, due to her believing that his hybrid status made him an "abomination". 

                       
Klaus was an English nobleman during the late 15th century when he met Katerina Petrova, the doppelgänger whose appearance he had been awaiting for five hundred years. Planning to use her in the ritual, he had kept her entertained until the full moon, but she learned of his plan before it could take place and escaped, taking the moonstone with her. As she fled, she encountered a vampire named Rose, whom she tricked into turning her into a vampire, thus ruining forever Klaus' plan to use her to break the curse. After Katerina turned into a vampire, Klaus assumed that her family line ended with her and that his chance to break his curse was gone forever. In retaliation, Klaus traveled to Bulgaria and murdered Katerina's entire family for her defiance.