|“||I'll have to explain this family to Hope one day. You know what I'll start with? Always and forever.||”|
Always and Forever is the vow that was made long ago by members of the Mikaelson Family, and members of Dahlia and Esther's Family Bloodline, specifically a promise made between Esther Mikaelson and her sister Dahlia in the late 10th century, during which they vowed to never leave each other's side. "Always and Forever" was then used as a promise again by Esther to her son Klaus many years later to assure him that she would always be there for him if he was scared. Later Klaus, Elijah and Rebekah made the same promise to stick together, after their family had split up following the death of their mother. This promise, in any iteration, has been broken sixteen known times in its history - 2 times by Esther in the late 10th century, 5 known times by Rebekah in 1919, in 2011, in 2012 and in 2013, 2 known times by Elijah in 2012 and in 2013, and 7 known times by Klaus in 1001, in 1835, in 1922, in 2010 (twice), in 2011 and in 2013.
In the 21st century, the original promise was renewed between Elijah, Klaus, Rebekah, and their brother Kol after they were reunited as siblings for the first time in years. Klaus reminded his maternal younger half-brother of this promise again in I Love You, Goodbye, when it became clear that Kol was dying from a hex. In Behind the Black Horizon, it is cemented that this vow also includes Finn and Freya.
In Ordinary People, flashbacks were shown of the late 10th century, when Mikael and his children were turned into Original Vampires. Upon being transformed into the first vampires, Mikael and Esther's children Finn, Elijah, Klaus, Kol, and Rebekah presumably all made their first human kills as a result of their hunger. However, when Klaus made his first kill, he unknowingly triggered his werewolf gene, which made him into the world's first Hybrid and revealed to all that he was not Mikael's son, but instead the son of the werewolf chief of their village, Ansel. In the aftermath of this revelation, Klaus' werewolf gene was bound with a curse by Esther, which he took as such a betrayal that he ultimately killed his mother in his rage and made it look as though Mikael did it. Afterward, Mikael, Finn, and Kol fled their village, leaving only Klaus, Elijah, and Rebekah to bury their mother. Knowing that Klaus was devastated by everything that happened after he was turned into a vampire, Rebekah and Elijah both assured him that they would never turn their backs on him like their mother did, and swore to stick together as one, "Always and Forever". This was a pledge and a promise that would often be repeated by the three Mikaelson children.
- "The promise of always and forever, as beautiful as it sounds on the surface, is often, for our characters on this show, a justification to do what they think they need to do, consequences be damned, collateral damage be damned."
- —Michael Narducci
In City Beneath The Sea, Dahlia shows her nephew her young adult memories of how this promise originated. There was a massacre led by the Vikings on her childhood village. Dahlia and Esther then hid behind a wheelbarrow, the two sisters promised each other that they would remain together no matter what happened, "always and forever". When a Viking found the sisters and attempted to attack Esther, Dahlia used her magical telekinesis to shove him away from her, which led the Vikings to take both girls prisoner rather than killing them like the rest of the villagers. The girls were taken to a nearby hovel, where Dahlia agreed to do the dark magic that the Vikings wanted from her to ensure that Esther wouldn't be harmed; instead, Dahlia took the abuse from the Vikings in Esther's place to protect her from most of the horrors of their situation.
One day, while toiling in the hovel while Esther picked herbs for her outdoors, Dahlia managed to stealthily infuse potent sage with serpent's blood to give herself and Esther the magical strength necessary to escape their captivity. However, when Esther returned and Dahlia explained her plan, Esther instead confessed that she no longer wanted to practice witchcraft because she had fallen in love with one of their Viking captors, Mikael, with whom she planned to marry and start a family. Dahlia was emotionally devastated by this revelation and begged Esther to stay with her, reminding her of their promise to stay together forever, but though Esther assured her they would always be sisters, she left despite Dahlia's pleas and married Mikael in 971. This later lead Dahlia's spitefulness towards her sister which isn't resolved for centuries.
In The Bloody Crown, amongst Klaus' trial, in an effort to make herself believable, references the vow made so long ago. Rebekah tells that she has been bound to Klaus all her life, not because they are family, or because she loves him, but because so long ago, they promised that they would never leave each other. She goes on to explain how this pact has stopped her from finding love or truly being "free". Although Rebekah is trying to sound believable, what she says is true.
- Though it was originally believed that the "Always and Forever" vow was created by Elijah and Rebekah, it was revealed in City Beneath The Sea, that it was actually a vow first made by Esther and Dahlia prior to their capture by Vikings, where they vowed to always stay by each other's side, come what may.
- Although in Ordinary People, only Elijah, Rebekah and Klaus were present during the making of the vow, it has been seen on more than one occasion that the vow also includes Kol and Finn.