One of the "vegetarian" vampires that lives in Denali, Alaska. Meyer claims that Kate and her coven of vampires (minus Eleazar) are the origin of the mythical Succubus. While that might fly fine in little Stephenie's Meyerverse, history trumps failogic in the end. She has the power to deliver electric shocks that can make people (both humans and vampires) collapse. She may or may not serve as a backup power source for her local electric grid. Her power is not effective against Bella, because apparently massive electrochemical changes in your nerves resulting in generalized convulsions are not physical. Alternately, perhaps Smeyer just has no bloody clue what on earth she's talking about. By the end of BD she is mated to Garret, which is probably for the best, in that he atleast seems to enjoy getting electrocuted for the heck of it.
Mythology does not approve of Meyer's shenanigans.