Werewolves with a Moonlight Ring do not need to transform to activate the bite
A Werewolf Bite is an ability of a werewolf or a vampire-werewolf hybrid to produce fangs which can be used to bite in an animalistic manner. This bite is fatal to vampires. While it was long thought to have been the bite itself, it is now discovered that is due to the extremely venomous toxins that are produced by the salvatory glands found in mouths of both werewolves and hybrids. The bite is usually used as a weapon by werewolves and hybrids against their vampire enemies, as it is one of the easiest methods of killing a vampire.
Werewolves
To werewolves, it can only be achieved when one transforms during the Full Moon. However, it can be activated at will through use of Moonlight Rings or evolving.
Hybrids
To hybrids, it is activated at will either in human form or in werewolf form due to their ability to fully control their transformations at will.
Effect
Klaus biting Will
Whenever a vampire is bitten by a werewolf or hybrid, the venom will be transmitted into the vampire's bloodstream from the werewolf's mouth. Once the blood is contaminated by the toxin, the vampire's heart will pump the venom throughout their entire cardiovascular and systemic circulatory system, during which time it will infect every cell in the vampire's body.
The length of time needed for the saliva to destroy the bitten vampire can vary based on several factors, such as whether it was a werewolf or hybrid who bit the vampire and how transformed the werewolf was at the time. After bitten by a very experienced and fully-transformed werewolf named Jules, the vampire Rose rapidly deteriorated until Damon Salvatore ultimately decided to euthanize her roughly a day afterward. On the other hand, when Damon himself was bitten by Tyler Lockwood, a new werewolf on his second full moon who wasn't fully transformed at the time (he was still fully-clothed in human form, with only his eyes and fangs having transformed), it took approximately three days for him to be on the verge of death.
A werewolf’s bite will also cause a vampire to hallucinate and go rabid as if it were a wild animal, causing them to lash out as their bodies went into survival mode in hopes that human blood would heal them. A vampire's death by a werewolf bite is very slow and painful, which is why many who are bitten are ultimately "mercy-killed" before they reach that point. Werewolf bites cannot kill an Original vampire, as Elijah Mikaelson mentioned to Elena Gilbert when they were talking about how to kill Klaus Mikaelson. However, it does weaken them temporarily, as Rebekah Mikaelson felt dizzy and had severe hallucinations after drinking a beer laced with a concentrated dose of hybrid venom. It wore off within hours; she just had to rest for a while for her body to metabolize it.
Toxin
Weaponised venom
In The Rager, it was shown that one can extract werewolf\hybrid venom by using a syringe inserted into the werewolf in question's gums to take a sample. From there, it can be used mixed in food or drink (such as when Connor Jordan injected it into a keg of beer that was delivered to Rebekah's party) or can be used to fill or coat bullets (such as when Galen Vaughn used werewolf venom-laced bullets to shoot Damon in Graduation), and it will affect any vampire who ingests it or is otherwise infected with it. Unlike werewolf bites, hybrid bites are fatal to vampires much more quickly-- typically a vampire will die or be on the verge of death within twenty-four hours, as seen in the case of Nadia Petrova.
The Cure
The only known cure to the bite of a werewolf is the blood of the original hybrid Klaus, though it is speculated that the blood of Klaus' daughter Hope could also be used. However, Dr. Wes Maxfield thought it possible to synthesize a cure from the venom of a werewolf itself although this theory was never tested. In While You Were Sleeping, the Travelers were able to find a cure for Elena, who was injected with a form of the Ripper compound that was laced with werewolf venom, suggesting that it is possible for science to create an antidote, but this too has yet to be discussed further. In I'm Thinking of You All The While, Kai used his abilities as a Siphoner to absorb the magic from the venom which nullified it proving that there is another cure from the venom besides the blood of Klaus, however, the vampire in question will have to be a siphoner-vampire hybrid. In You Hung the Moon, another cure was shown when Lucien injected an unknown substance into himself eliminating the effects of the bite from Jackson. Presumably, this is a synthesized version of the cure.
Humans
It has not been shown how a werewolf bite would affect a human in the case that they are attacked (which is unlikely due to their ferocity and above-vampire prowess). When the supernatural vampire hunter Connor laced the keg of beer at Rebekah's party with werewolf venom, quite a few humans drank it with seemingly no consequences, so it can be presumed that werewolf venom itself has no effect on typical human beings. Klaus fed on the human Camille O'Connell in Après Moi, Le Déluge and she felt fine afterwards.
Vampires bitten by Werewolves/Hybrids
Trivia
- Damon, Elena and Rebekah are the only main vampires who have suffered the effects of werewolf venom without actually being bitten by a werewolf or hybrid (Though Damon had also been bitten by a werewolf prior to that experience)
- Damon mercy-killed Rose and Will before the effects of the werewolf bite could be fatal.
- Nadia Petrova is the first and only vampire shown on screen to die solely due to a werewolf/hybrid bite so far.
- It was speculated by Wes Maxfield that because werewolf venom is a toxin, it could presumably have an antidote created by scientific means rather than Klaus' blood. However this was never proven only mere speculation.
- In While You Were Sleeping, the werewolf-venom-enhanced Ripper Compound that Elena was injected with was later cured thanks to the antidote created by an ally of the Travelers and delivered by Enzo. This suggests that a scientific cure for werewolf bites may be possible.
- Mikael, like the rest of the Original vampires, cannot be killed by werewolf bites. However, he demonstrated in Live and Let Die that because of his indomitable will and warrior instincts, he is capable of fighting through the effects of the werewolf venom with great focus. As a result of this ability, he was able to recover from the bites much faster than his children Elijah and Rebekah did when they were infected with the venom. In From a Cradle to a Grave, Mikael drank the blood of vampires who had been bitten by numerous werewolves with little to no negative effects, as well.
- A Siphoner is able to siphon the magic from the bite.
- The same applies to siphoner-vampire hybrids who, although remain affected by it, can cure themselves through siphoning.