Werewolf

Werewolves (also called Lycanthropes, Loup Garou, Rougarou, Beasts, or even just Wolves for short) are a supernatural shapeshifting species of individuals who unwillingly transform into large, fearsome, and extremely hostile wolves on the night of the full moon. They were created by the witch Inadu as revenge against her tribe for killing her. Even in their human form, werewolves possess superhuman physical prowess, though not to the same level as a vampire, and their abilities are not as powerful compared to those they possess on the full moon while transformed. These creatures are the most dangerous enemies of vampires due to their venomous bite, which is lethal to them. Werewolves are also hardwired to kill vampires on sight in their wolf form, though they still hunt human prey whenever there are no vampires to kill.

Triggering The Werewolf Gene.
Lycanthropy is an inherited genetic condition due to a curse, and a person can only be a werewolf if they are born to at least one werewolf parent; they cannot be turned by a bite or scratch. Furthermore, the werewolf gene must be "triggered" by taking the life of a human, either intentionally or by accident, in order to gain access to their enhanced physical abilities, though this comes at the cost of transforming into a wolf during every full moon. It does not matter if the kill was accidental or intentional, premeditated or out of self-defense — if a werewolf causes the death of a human in any way, their werewolf gene will be activated. Untriggered werewolves, however, can kill vampires without activating their curse.

Because difficult-to-control anger and aggression are common personality traits in even those werewolves who have not activated their lycanthropy, the likelihood of them losing control of their rage and inadvertently triggering their werewolf gene by accidentally killing someone is quite high; it is even speculated that the anger and aggression inherent in werewolves is intended to increase the likelihood that a werewolf will activate their lycanthropy. However, it is possible for an untriggered werewolf to go their entire life without killing; in fact, this happens frequently enough that in some cases, a family's lycanthrope heritage will be kept a secret that will ultimately die with an ancestor, causing the knowledge of their heritage to be lost and remain unknown for generations that follow until a member takes a life and unintentionally triggers their curse; this has happened at least twice in the Lockwood Family's history.

After the gene is triggered, the werewolf's eyes will turn black and gold, and their latent powers (such as increased strength and accelerated healing) will activate instantly; from then on, they will be cursed to painfully transform into a wolf on the night of every full moon (although there are unique circumstances that will prevent a werewolf from having to turn, such as pregnancy (in the case of females), being an Evolved Werewolf, or possessing a Moonlight Amulet). A werewolf who has yet to trigger his or her curse only exhibits one characteristic of lycanthropy: increased aggression and anger on a general basis, which can become overwhelming fits of violent rage leading up to and during the nights of the full moon. Also, until their werewolf genes are activated, untriggered werewolves can be compelled by vampires just like any human, as proven when Damon Salvatore was easily able to compel away Tyler Lockwood's memories of seeing Vicki Donovan "vamped-out" before Tyler had triggered his werewolf gene. After the gene is triggered, however, they become immune to vampire mind control.

History.
In Voodoo in My Blood, the origins of the Werewolf Curse and Werewolves were revealed. A powerful witch, that was known as "the Hollow", cursed the members of her tribe that were responsible for her murder and created the Seven Werewolf Bloodlines. The Hollow was hunted by wolves, and was killed on the night of a full moon. These circumstances would cause future werewolves to have to take a human life to activate the werewolf gene, forcing the species to have to painfully shapeshift on the night of a full moon into the very animals that hunted Inadu down.

The Middle Agesedit
Werewolves actively populated the New World during the early Middle Ages during the time that Viking invasions began in Europe. Many villages across the land were highly populated by werewolves and they lived along side one another in villages. They also lived alongside humans, although to protect their human and untriggered loved ones, the wolves made sure that they had access to natural means of protection during the time that they were changed. One of the most notable locations of a werewolf village was in what is now present-day Mystic Falls. Beneath the area was a series of tunnels that provided protection for the humans while the werewolves were turned on the full moon. One clear rule of the village was that the humans were forbidden from being around the wolves while they were transformed for their own safety, as the majority of werewolves are unable to control themselves when transformed and could easily maim or kill any non-werewolf species in their vicinity.

A notable event in the history of the werewolves comes with the arrival of inhabitants of the "Old World," where a plague had been devastating the population. The newcomers included Mikael, his wife Esther, and Esther's witch mentor and friend, Ayana, as well as Esther and Mikael's young sons Finn and Elijah. Having lost their first-born daughter Freya, the sister of Finn and Elijah, in Europe, Mikael and Esther wanted to be able to raise a family in a place free from illness, and Ayana eventually led them to the New World where they could live in peace. The villagers accepted the new family and they became an integral part of the village life, with Ayana acting as the local healer and the conduit to the Spirits. Mikael and Esther, desperate to rebuild their family after the loss of Freya, eventually conceived and gave birth to Niklaus, Kol, Rebekah, and Henrik, who followed their eldest brother Finn and second-eldest brother Elijah.

However, when Henrik and Klaus broke their village's rule one full moon night and went to watch the wolves turn, Henrik was accidentally attacked and killed by the turned wolves. Determined to not lose any more family, but also not wanting to move away again, Mikael convinced Esther to tap into Dark Magic to perform a modified version of the witch Qetsiyah's Immortality Spell in order to turn Mikael and their children into nearly-invulnerable beings. Once turned, Mikael and their children gained enhanced strength, speed, reflexes, and healing superior to the werewolves that would ensure their protection from their supernatural neighbors, and their new species eventually became known as the Original vampires. However, the ritual had unexpected side effects, and the newly-turned family's lust for blood eventually led them to inadvertently shatter the peace of their village, as their lack of control over their newborn vampire hunger led to them being unable to resist feeding on the innocent inhabitants of the town.

Shortly after being turned into a vampire, Klaus made his first human kill, which resulted in Esther's darkest secret coming to light; Klaus was not Mikael's son, but instead was the product of an affair Esther had with the Alpha of their village's werewolf pack, Ansel. Killing a human activated Klaus' werewolf gene, which turned him into the world's first werewolf-vampire hybrid. Furious at his wife's betrayal, Mikael slaughtered Ansel - whose pack was also responsible for Henrik's death - along with half of the remaining werewolves in their village, igniting the war that still exists to this day between the werewolves and the vampires. However, enough of Ansel's family survived the attack to continue the bloodline, which still exists into the 21st century.

Modern Timesedit
According to Jackson Kenner, at least two werewolf packs have been around since what he calls the "beginning," which could be referring to the genesis of the werewolf race - the Crescent Wolf Pack and the North East Atlantic Pack. In Home, the magic purification spell that the Travelers performed to break the Travelers' Curse and undo Spirit Magic and other non-traditional forms of magic resulted in Tyler Lockwood's werewolf gene being deactivated. This returned him to an untriggered werewolf, though it did not lift the curse completely.

In The Brothers That Care Forgot, it was revealed that the werewolves' power can be traced back to the myth of the Unification Ceremony, a ritual that bestowed certain unique abilities onto every member of a pack. At the earliest point of their existence, each werewolf bloodline was distinct — some had speed, some had strength, and some could sense their enemies from miles away, presumably among other unique abilities. It was only after a few centuries of intermarriage that all werewolves ended up having the same powers, which is why there is a lack of diversity in werewolf abilities in the modern age.

Werewolf Genocideedit
After Mikael decimated the werewolf community in the northeast Atlantic region of the New World, and after Esther died at Niklaus' hands out of rage at her betrayal, the Mikaelson siblings returned to the "Old World" and began traveling from country to country as they followed the Normans, feeding on the locals and turning new vampires as they went. The war between vampires and werewolves came to a head at some point in the centuries afterward, when the vampires discovered that the bite of a werewolf was lethal to their kind. This spurred the vampires to preemptively commit mass murders of werewolves to protect themselves from death at their hands. As a result, the werewolves were driven to near-extinction by these massacres, and vampires who were turned in the period of time following this Werewolf Genocide began to believe that werewolves were nothing more than a myth or legend.

In reality, many werewolves had survived the genocide, keeping their supernatural identities a secret as they began to reorganize themselves into packs in order to help them evade the vampires. These packs, which varied in size from one dozen members to upwards of a hundred, also helped give the werewolves a support system to assist them through their very painful transformations each month during the full moon.

Even still, the mass killings of werewolves has continued on into the modern day, beginning with Niklaus Mikaelson's attempt to create an army of werewolf-vampire hybrids using his blood and the blood of the human doppelgänger, Elena Gilbert, which caused the deaths of dozens of werewolves who then transitioned into werewolf-vampire hybrids themselves. Additionally, a large population of werewolves continues to live in the area surrounding New Orleans, Louisiana, USA. Due to the tensions that exist between the witches, the werewolves, the vampires, and the humans, the werewolf community continues to experience a significant death rate as a result of the infighting between factions.