Tatia ~ "When your mother asked for my blood, she said nothing of the dark magic that would turn you into a monster!"

Tatia was described as the most pure out of all the Petrova doppelgängers. She also, in her brief appearances, seemed to be outgoing and inclined to live life to the fullest, judging by the fact that she refused to kill herself after her Viking husband's death, and instead chose to live in order to raise her child and hopefully find love again. Tatia did not believe in fate, and refused to let the concept "dictate" her heart. She believed in choice, much like her descendant Elena.

She was a Petrova doppelgänger with whom both Niklaus and Elijah Mikaelson fell in love in the late 10th/early 11th century. She is the first doppelgänger to be created from Amara's line after she was turned into a true immortal in the 1st century B.C. Elijah and Niklaus' mother used Tatia's blood to turn them into the world's first vampires, which eventually lead to her death at the newly-turned Elijah's hands. After her death, her blood was used in the spell that bound Niklaus' werewolf heritage.

During the Middle Ages, Tatia lived in a small village with her husband and their child. However, he ultimately died in battle, and instead of throwing herself on his funeral pyre as was expected of a Viking widow, she decided to live, move on and try tofind love again. Later in time, she met both Elijah and Niklaus, both of whom fell in love with her. However she eventually chose Elijah. Esther, the mother of Elijah and Niklaus, used her in the spell to create the Original Vampires, after the death of her son Henrik at the hands of the werewolves in their village. Tatia's blood was enchanted by Esther and mixed with the wine that she and Mikael gave their children with dinner.

After the Mikaelson children's transformations, Klaus made his first human kill and activated his werewolf gene, which also revealed he was actually the illegitimate child of Esther and a werewolf villager named Ansel. When Klaus awoke the morning after his first transformation as a hybrid, he was tended to by Elijah, though, unknown to either of them, Tatia had followed them into the woods to see what had happened. What led her to them were body parts of six villagers torn away in Klaus's wake. Tatia eventually saw Klaus covered in blood and ran away in fear causing Elijah to chase after her to explain to her what had happened. While she was fleeing from them Tatia tripped and cut her hand badly in the process.

Tatia told Elijah to stay away from her as she scrambled to her feet and then asked him what he was. Elijah promised her that he loved her and he was the same man she fell in love with. She told him that despite Esther asking for her blood she had no idea Esther was planning on using it to turn Elijah into a monster. Elijah told her he wasn't a monster however in the middle of saying so he smelled Tatia's blood. She looked down and turned over her hand to reveal the cut and the blood. Tatia slapped Elijah across the face hoping to protect herself and to make him come to his senses. He told her that he would not harm her. However the smell of fresh blood over powered him and he begged her to run. Finding that she would be unable to stand and fight she ran from him again. Though this time when Elijah chased her he caught up to her and even with her struggling to get him off her he bit into her carotid artery on the right side of her neck as she screamed and began to pass out from blood loss.

Afterward, Elijah came back to his senses and realized what he had done and desperately brought her to his mother in hopes that she could save her. However Tatia had died and Esther assured him that she would take care of it. She cast a spell on Elijah to help him repress his memories of killing Tatia. Which put his memories of the act behind what Elijah refers to as his "red door." Esther then used the rest of her blood to cast the Hybrid Curse on Klaus in order to bind his werewolf side and help restore the balance caused by the immense power he had gained from being both vampire and werewolf. Elijah and Klaus then went on believing that Esther had killed Tatia in order to cast the curse until Red Door, when Esther admitted to Elijah that he, in fact, was the one who killed Tatia. Elijah then confessed to Klaus that he had been the one to kill their beloved Tatia in Brotherhood of the Damned, a sin for which Klaus ultimately forgave.