Corin

Corin is a female member of the Volturi guard, whose first appearance was in the vampire index in the back of Breaking Dawn. She has the power to make others feel content with their situations. Because of this power, she is frequently assigned to keep Sulpicia and Athenodora company, but she is also ordered by Aro to keep Chelsea from leaving the coven, since her power can make others feel physically uncomfortable when they are not exposed to it for a period of time.

Early life
Aro hoped that she could help Marcus recover to some degree from the loss of his wife, but when Marcus refused to accept Corin's gift to ease his pain, Aro found her gift more useful in consoling the Volturi wives. Corin then spent most of her time associating with the wives, and is also the reason to why they never leave their tower, as mentioned in Breaking Dawn.

In the Volturi, Corin's responsibility is to protect the wives of Aro and Caius, Athenodora and Sulpicia. However, she doesn't guard them so much as ease them into complacency while other, more physically imposing guards do the actual job of protecting the wives. The wives are so closely guarded that they have become virtual prisoners in Volterra. However, Corin's ability keeps them satisfied with life.

Aro also instructs Corin to use her gift on Chelsea, the highest ranking member of the Volturi, making it nearly impossible for Chelsea to leave the Volturi, because of the drug-like side effects that inflict on her if she isn't constantly exposed to Corin's power. Marcus has repeatedly refused to allow Corin to relieve his pain over Didyme's murder. Aro is also careful not to expose himself too greatly to Corin, while Caius frequently uses Corin's gift to mitigate his boredom between punishing expeditions and battles.

Breaking Dawn
In Breaking Dawn when Irina reports to the Volturi about an immortal child, an illegal creation, being created in the Cullen family, the entire Volturi coven departs to destroy the child, only to later find out that she is actually a half-human half-vampire hybrid.

Since the entire Volturi coven travels to Forks for this act, there is no doubt that Corin is among them.

Powers and abilities: addictive contentment
Corin is gifted with the supernatural talent of inducing in others feelings of contentment for his or her situation. Her talent can be comparable to that of Didyme's "happiness induction"; although rather than bringing out the positive feelings of happiness and joy, Corin instead brings out feelings of contentment and ease in a person, despite his or her situation. There is a drug-like side-effect to her gift to those who experience it often, as they may begin to feel unwell and uneasy without it.

Although it is not explained whether this gift is mental or physical, by the way it works it may be assumed to be a more physical gift, working similarly to Jasper Hale's empathy.

Appearances

 * Breaking Dawn