Sancar was a Turkish vampire who wanted to build a vampire harem. He searched for unusual women for his collection throughout all of Europe with his humans for servants. He managed to find and turn seven of women, but found no one who could completely capture his interest until, while in Ireland, he heard whispers about Siobhan's beauty and strength.
He sought her out and was excited to find a woman like none he had seen before; she was amazingly beautiful and stronger than most men in her village. He abducted her in the middle of the night, raped her, bit her, and then took her back to his home while she was experiencing the painful transformation, after which he found it quite difficult in dealing with her as a newborn vampire. Siobhan was incredibly strong, even for a newborn, with no love for him. He tried to keep her distracted with ample amount of blood, but before her first year passed, she killed him and three of his devoted followers, splitting apart the harem.
Sancar's existence is only mentioned in The Twilight Saga: The Official Illustrated Guide.