Riley Biers was the second vampire created by Victoria after her mate James was killed by the Cullens. She convince him that they were mates and manipulated him to do her biding. When Victoria began turning others for added protection, he became her mouth piece. He was able to keep the other newborns in control because he had to power of Persuasion.
When it was time for the army to attack the Cullen Family and Bella, he obtained Bella's scent for the newborns, and was the one that led the Seattle newborn army. During the invasion, he stayed with Victoria until he was killed.