Alaric Saltzman

Dr. Alaric J. "Ric" Saltzman is a main character of The Vampire Diaries and Legacies. He is a former recurring character of the first half of Season One, Season Four and Season Five. He was also a recurring character on The Originals, first appearing in the eighth episode of the fourth season. He also served as the main antagonist in Season Three along with the Mikaelson Family. Alaric is a human, vampire hunter, former history teacher at Mystic Falls High School and a former Enhanced Original, not by being one of the first vampires as the Mikaelson Family is, but instead being turned through an altered version of the spell used on the Mikaelson family. 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 a teenager, a daughter named Elena Gilbert, his student. Alaric began a romantic relationship with her adoptive aunt, Jenna. Following Jenna's tragic death, he seemed to step into his step-father role to Elena and is a father figure to her brother, Jeremy. He is also Damon's best friend alongside Bonnie; Damon even called Alaric "brother" on occasions.
Through overuse of the Gilbert Ring, Esther manipulated his spirit while he was on the Other Side before he would resurrect, and as a result he developed an alter ego, called The Darkness by Bonnie and Dark Alaric or Evil Alaric to others, that hated vampires and vampire sympathizers; as the Darkness, Alaric killed several members of the Town Council. With a goal to create a monster to end all monsters — similar to her husband before him — Esther linked Alaric's life force to Elena's and, in the process, created an Enhanced Original Vampire with one true weapon, the final, indestructible white oak stake. Fearing for her family's life, Rebekah Mikaelson caused Elena's death, thereby killing Alaric in the process. Following this, Alaric was resurrected as his Original vampire self without his alter-ego. While trying to save Damon from Tripp Cooke, Alaric was pulled into the magic purification zone over Mystic Falls. He temporarily died from the stab wound that killed him before his transition, when the magic that made him an Enhanced Original was stripped from his body. Jo Parker revived him with her medical skills, but upon resurrection, Alaric reverted back to his human self.
As a vampire hunter, he designed several different weapons to fight vampires which include vervain tranquilizers and arm vest stakes.
As a Ghost, he watched over Damon, Jeremy, and Elena. In the last two episodes of the fourth Season, his spirit was brought back into the world of the living (albeit confined within the Expression Triangle) where his presence proved crucial at offsetting the threat of the Hunters of the Five in their goal to kill Silas after curing him of his Immortality. His ghost was resurrected in Home, from the Other Side before its destruction, being the last to cross over to the land of the living.
After being resurrected, and though he retained his status as an Enhanced Original Vampire, he became a college professor at Whitmore College, teaching Occult Studies (taking up the same position that was held by both Sheila Bennett and Atticus Shane). He met and fell in love with Josette Parker, who saved his life when he crossed the magical border into Mystic Falls which stripped him of his supernatural powers and made him human again. Eventually, they came to find out that they were expecting twins. However, Josette was brutally murdered by Kai Parker at their wedding, seemingly along with their unborn children. 
Alaric later became a father when his children, Lizzie and Josie, were saved by the Gemini Coven and carried by Caroline Forbes. They would later set up a home together and eventually became engaged. However, Stefan returned and they had to rejoin the supernatural world in Mystic Falls. Caroline broke off their engagement and Alaric helped Peter Maxwell and Dorian Williams at the Armory with the mystery of Sybil and the return of Katherine, who wanted to destroy Mystic Falls. When Mystic Falls was saved, Alaric, along with Caroline, set up the Salvatore Boarding School for the Young & Gifted. 
Alaric is a member of the Saltzman Family and a non-biological relative to the Petrova Family and the Gilbert Family, due to being Elena's step-father through his marriage to Isobel, and Jeremy's guardian.