- "Chelsea can influence the emotional ties that people feel toward one another either by strengthening their bonds or breaking them apart."
- ―Entry on Chelsea's gift[src]
Chelsea can both increase and decrease the emotional ties between people. She can make partners turn away from one another, disband covens and friendships, but also can strengthen the bonds between people and potentially create new ones.
The effects of Chelsea's power are long-lasting and fade depending on how long a person has been exposed to it. Someone could form a bond (or lack thereof) to someone for decades or centuries before Chelsea's gift starts to wear off.
Chelsea cannot as easily influence the emotional ties of people when those ties are stronger than just friendship or acquaintance. For example, she could not have changed the way Edward and Bella felt about each other, and she also was not able to break Eleazar's bond with Carmen when he decided to leave the Volturi. Her power is psychic, as proven when she tries to bind Bella, Edward, Benjamin, Zafrina, and Kate to the Volturi during the interrogation in Breaking Dawn, but is unsuccessful due to Bella's mental shield. Eleazar also suggested that abstaining from human blood allows vampires to form deeper bonds to overcome Chelsea's influence, though this was never proven.
Since Aro kept Marcus, who can sense the emotional bonds between individuals, but not influence them, it is possible that Chelsea's power only involves manipulating and not recognizing the bonds first hand.
It is not known if Chelsea could influence people as a human, but according to Carlisle's theory about how every vampire brings their most dominant trait over when they are changed, she may have been able to.
Chelsea had since lived with the Volturi as the center of their organization and wears the darkest of cloaks along with Jane and Alec to represent her superiority. She had also bound the relationships within the Volturi to make the members work more effectively as a whole; Caius was kept from attempting to rebel against Aro; and Jane and Alec were made to never question Aro's, or any of the leaders', motives.
Whenever the Volturi (specifically Aro) offer a vampire a place in the guard, Chelsea makes the vampire feel bonded to the Volturi and severs the previous bonds he shared with other vampires or humans. This makes it extremely difficult to refuse any offer from them. Demetri, Renata, and Heidi are examples of this.
Chelsea is also very important when the Volturi are in a fight, as she separates the allegiances between covens so that the Volturi can defeat them more easily. If Aro has an interest in some of the opposing vampires, he would also use the opportunity to steal them.
- "There is one among the guard. Her name is Chelsea. She has influence over the emotional ties between people. She can both loosen and secure these ties. She could make someone feel bonded to the Volturi, to want to belong, to want to please them…"
- ―Edward's description of Chelsea's gift.[src]
In Breaking Dawn, Chelsea tries to sever the bonds between the Cullens and their allies, but Bella's shield repels her power. At Aro's urging, she tries again to bind Bella, Edward, Zafrina, Benjamin and Kate to the Volturi, but like before, it fails also. This marks the first failure of her influence.
- Didyme could impact others with her gift of happiness induction, making everyone around her naturally cheerful and happy.
- Jasper Hale has the power to sense and control the emotions of those around him, which can be used as a means of bonding, though his power is only effective for as long as he is present.
- Marcus's gift is similar to Chelsea's in a way that he can identify the emotional bonds between people and find their weaknesses.