Denali coven

"Behind my human friends were my new cousins-in-law, the Denali vampire clan. I realized I was holding my breath as the vampire in front — Tanya, I assumed from the strawberry tint in her blonde curls — reached out to embrace Edward. Next to her, three other vampires stared at me with open curiosity. One woman had long, pale blonde hair, straight as corn silk. The other woman and the man beside her were both black-haired, with a hint of an olive tone to their chalky complexions."

- Bella upon meeting the Denali Coven

The Denali Coven is a coven of vegetarian vampires comprising of Kate, Garrett, Carmen, Eleazar, and Tanya. The Denalis are one of the two known vegetarian vampire covens in the world, the other being the Cullen family. They are very close to them, being one of the Cullens' most loyal allies, going so far as considering themselves their extended family. The Denali Coven is located in Denali, Alaska, which, along with their vegetarian diet, allows its members to live alongside humans without too much trouble. It is said that this diet makes a vampire more civilized and capable of real love.

History
The coven originated in Slovakia and consisted of Sasha and her "daughters", Tanya, Kate, and Irina, all three were changed around the same century. At an unknown time, Sasha secretly created an immortal child, Vasilii. When the Volturi found out, they came to destroy the entire group, but Aro decided to spare the sisters, since they knew nothing about the child. Sasha and Vasilii were destroyed in the process.

The three sisters then searched for pleasurable company of men to deal with their loss, and subsequently are the originators of the "succubus" legend; a creature in the form of a beautiful woman who has sexual intercourse with men before killing them. Eventually, they grew lonely over the years by the scarred pain of their deceased mother and some of the men they'd killed. Tanya decided to try a vegetarian diet to see if she could gain control to avoid killing men while sleeping with them. The method proved effective, and Kate and Irina joined her. The sisters then relocated to Denali for its wide population of animals, and they learned to avoid killing men during sexual intercourse over the centuries.

At some point, Carmen and her mate Eleazar, a former guard to the Volturi, found the three sisters and stayed with them to test their lifestyle, eventually joining their family. Also at an unknown time, they met the Cullen family, and the two covens became strong allies and close friends, though they preferred to think of each other as cousins due to their similar diet. Tanya developed romantic feelings for Edward Cullen, but he did not reciprocate.

Midnight Sun
In the partial draft of Midnight Sun, Edward comes to stay with the Denalis after his first uncomfortable encounter with Bella Swan (see Twilight). Tanya is initially led to believe that he has decided to return her feelings, but he tells her that it is not so. Despite this, she continues to pursue him, eventually leading to Kate and Irina telling her that she is annoying Edward. After six days, Tanya persuades him to find the courage to face his problems, encouraging him further by saying that he is that type.

New Moon - Eclipse
A vampire named Laurent comes to stay with the Denalis after recently leaving a coven of non-vegetarian vampires, and is ready for a change in his life, which happens when he and Irina fall in love. At one point, however, he returns to Forks as a favor to his old friend, Victoria, to 'get the lay of the land for her' so that she can hunt Bella Swan. While he is there, he runs into Bella in the middle of hunting. When he is about to kill her personally, a pack of shape-shifters, who the Cullens happened to have a treaty with, kill him before he could get to her. Two months later, the Cullens call for aid from the Denalis after finding out that Victoria is creating an army of newborns to destroy the Cullens and kill Bella. The Denalis agree to help them, but at Irina's request to avenge Laurent's death by wiping out the shape-shifter pack. Carlisle refuses to allow this, and the Denalis abandon their long-time friends. The Cullens are forced to form an alliance with the shape-shifters instead, and successfully kill Victoria and destroy her army.

Breaking Dawn
The Denalis later feel terrible about abandoning the Cullens. Soon after the battle, the Denalis, except Irina, attend Bella and Edward's wedding and meet Bella for the first time. In the film, Irina does attend the wedding but leaves quickly (before the rest of her family) after noticing that the Cullens invited Seth to the wedding.

A few months later, Irina decides to visit the Cullens and finally make peace with them about Laurent's death. When she arrives in Forks, however, she sees Bella hunting with her shape-shifter friend, Jacob Black, and Renesmee Cullen, who appears to be an immortal child. Remembering Sasha's fate and her anger at the Cullens for not avenging Laurent's death, she goes to the Volturi and reports the Cullens' "crime". The rest of the Denalis are once again called upon by the Cullens for aid. Renesmee, the child Irina had seen, is really Bella and Edward's half-human half-vampire daughter. The Denalis, after some persuasion, agree to testify this for the Cullens against the Volturi. Kate, Eleazar, and Tanya also help Bella practice her power and fighting skills to prepare her for the potential battle.

When the Volturi arrive, Irina realizes she had been wrong. After admitting this, Caius has her killed to try to provoke a fight. His efforts fail, and the Volturi depart after Aro decides Renesmee is not a threat. With the Volturi gone and the situation resolved, the remaining Denalis return home to Denali, with their newest member, Garrett, who has joined them due to his romantic attachment to Kate.

Denali Coven extension
On the basis of their similar diet, the Olympic Coven is considered a loyal extension of the Denali coven, calling themselves cousins. In Breaking Dawn, Tanya apologizes for not aiding the Cullens in the newborn army crisis and states that she and her coven mates are part of the Olympic Coven too. The Olympic Coven consists of Carlisle Cullen, his wife, Esme; their adopted children, Edward, Alice, Emmett Cullen, as well as Rosalie and Jasper Hale; Edward's wife, Bella, and their hybrid daughter Renesmee Cullen.

Succubus legend
The Denali Coven's female vampires, with the exception of Carmen, used to lure men to their death by seducing and engaging in sex with them before feeding on their victim. However, on the long term, the strain wore on them and the Denalis started to feed on animal blood. They, however, kept enjoying the company and nocturnal activities with men, both vampire and human, which by now could survive the experience. This may also be the origin of the succubus myth: a demon that assumes a woman's aspect seducing men to have sex with it.

Trivia
The Denali coven is the third largest vampire coven in the Twilight Saga, comprising five vampires. Including the deceased members, the tally goes up to nine members.