Jane and Alec are the Volturi's most offensive weapons as they both hold abilities capable of taking down an opponent, regardless of size. Alec possesses the gift of sense deprivation. He can completely cut off all senses of multiple targets.
While Jane is useful in making an audience fear the Volturi, Alec is their most offensive weapon.
Alec was born in England around 800 A.D, the son of an Anglo-Saxon woman and a Frankish soldier. He was born a few minutes after his twin sister, Jane. Both Alec and Jane had strong psychic abilities that were evident even in their human state.
Aro had shown interest in Alec and his sister since they were toddlers, but decided to wait until they were old enough to turn them (the Volturi had already instated its rules about immortal children) and so left them in the care of their parents. Their talents had not taken a focused shape at that point, but bad things happened to people who were unkind to the twins or their family, and good luck followed those who were friendly to them. Eventually, the superstitious locals found the twins too frightening to endure. They were accused as witches and condemned to be burned at the stake.
Aro was apprised of the situation by a nomad who knew of Aro's interest in the twins. Aro hurried to the village, arriving just in time to interrupt the execution. Transformed at the age of about 12 or 13, they are the smallest and youngest in appearance as well as the most prized members of the guard due to their incredibly powerful gifts. It is said that they are the cornerstone of the Volturi's offensive abilities.
About one decade after they joined the coven, Alec and his sister displayed their powers for the first time in battle and annihilated the Romanian coven's army of over one hundred recruits.
Though not directly said, they could be considered two of the most powerful vampires in the world gift-wise, capable of taking down opponents regardless of size or age.
- ―Alec on Bella Swan[src]
Alec first appears in New Moon when Jane brings Edward, Alice and Bella, and Alec takes delight in teasing Jane for bringing back Alice and Bella instead of just Edward. Once Edward, Alice, and Bella are permitted by Aro to leave, they are taken to another room to wait until midnight in order to avoid suspicion. Alec is the guard who goes to inform them when they were allowed to go.
In the movie adaptation, Alec remains quiet in most of his screen appearance. He keeps hold of Bella while Aro decides what to do. When Aro makes his decision to kill her, Alec casts Bella aside, turning her around to face Felix, and walking out of the way. It is then Edward jumps in to protect her.
Alec does not appear in the book Eclipse. His twin, Jane, is sent to clean up the newborn army that Victoria created to destroy the Cullen family and Bella. It is said that only five members of the Volturi came: Jane, Demetri, Felix, and two other vampires.
Though he has no role in the book, Alec appears in the film adaptation of Eclipse. In the film adaption Alec appears in two scenes. In the first scene the Volturi are in Seattle checking on the newborn situation, Alec says, "Then decide sister, it's time." He puts his hand on his sister's shoulder as he says this. In the second scene the Volturi appear in Forks after the fight between the newborn army and the Cullens.
Added by Darkvoid12:"His gift is slower than Jane's. It creeps. It will touch us in a few seconds."
- ―Edward explaining Alec's gift to Bella.[src]
Alec appears towards the end of Breaking Dawn, and plays a larger role. He, alongside his twin, Jane, accompany the rest of the Volturi guard to Forks. They went to deal with the presumed immortal child, Renesmee Cullen, who is actually Bella and Edward's biological child. Jane and Alec attempt to use their powers to give the Volturi an advantage. When Jane tries to attack Bella after she blocks her powers, Alec holds her back, soothing her by patting her on the shoulder. After Jane's power gets blocked by Bella's shield, Alec tries to use his power. He is also unsuccessful, though he isn't angered by failing to penetrate her shield. He doesn't retract his "mist", but rather continues to look for holes and weak spots in Bella's shield, without success.
When the Cullens and their witnesses prepare themselves to fight against the Volturi, Vladimir states that Alec owes him many lives, and chooses Alec as his target. After Renesmee is proven to be a human-vampire hybrid by Alice's new witness, Nahuel, who is also of her kind, Alec retreats to Volterra along with the rest of the Volturi.
Added by Darkvoid12In Breaking Dawn - Part 2, Alec chases down Carlisle's Japanese friend Toshiro to allow Aro to interrogate him. At the clearing, he witnesses Jane's inability to attack the Cullens and their allies, and begins to use his power. However, before his black mist reaches far, Aro restrains him.
In Alice's vision of the battle, Alec kills one other vampire. As he is seen on top of another person who is no longer fighting back. Then, Alec occupies Bella to keep her from using her power, but then gets killed by Emmett, who severs his head from his body. The battle doesn't commence, however, and Alec lives.
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