- "No one does rebellion like the Irish."
Liam was an Irish warrior who fought in the Irish Rebellion of 1641, and later against Cromwell's reconquest of Ireland. Liam became a vampire through one of the most common types of accidental transformation: battlefield excess. It was common for nomads to seek out human wars as an opportunity to feast. Once a vampire was totally sated, they might continue to feed for enjoyment rather than need. They might not drain enough blood from the victim to kill, and thus the victim would begin the transformation process.
Liam met Siobhan during the first six months of his vampire life where she instructed him on vampire rules, thereby stopping him from drawing attention from humans and the Volturi. Liam was very taken with Siobhan's strength and beauty. They joined forces quickly and became mates. Liam can be selective about his prey, and English soldiers are still his preferred victims after centuries of killing Englishmen.
When they found Maggie, Siobhan wanted to make a supernaturally talented vampire of her own, but Liam was opposed to the idea. Partly because he did not want the Volturi to resent the imitation, and more importantly, he did not want to share Siobhan's attention with anyone else. However, she pleaded him to let things play out in time and give Maggie a chance, and he reluctantly agreed. Over time, he came to accept Maggie as part of the coven and considers her as a sister.
- Main article: Breaking Dawn
Liam is present when his coven help defend Renesmee Cullen and the Cullen family from the Volturi's accusation. Because Maggie declares the Cullens' truthful words, he and Siobhan believe their story absolutely and agree to help. He mostly remains in the background, never speaking but hovers around his coven and the Cullens. After the situation ended peacefully, Carlisle asks Liam and Siobhan to locate Alistair, the nomadic vampire who fled before the confrontation, to inform him how it turned out.
He is described as a man in his mid-30s, with a hard-face, lean body with an imposing countenance, and is 6'5" tall, and with dark brown hair. In the movies, he has a stubble, though he appears overweight than imposing.
Liam is usually very quiet, and very possessive of Siobhan, his mate. He can, however, be kind. While hunting, he mostly prefers to prey on English men due to his history with them. He is also described as very fierce and focused during a hunt, which manifested clearly when he was still a newborn. Unlike Siobhan, he was not as fascinated by the stories of supernaturally talented vampires, but learned to grow fond of Maggie, who has the ability to sense if someone was lying.
- Main article: Siobhan and Liam
Siobhan is Liam's mate. He is mentioned as constantly near Siobhan and following every order she gives him.
They first met when he was still a newborn, and she took him under her wing to teach him everything he needed to know about being a vampire, including the cons and the pros. Eventually, they fell in love and traveled together.
Maggie is the third member in the coven.
When Siobhan first decided to change her, Liam was reluctant to the idea of sharing his mate's attention with another, but Siobhan managed to convince him to give it a chance. He reluctantly agreed to please her, but after some time, he grew to like Maggie and began to see her as a little sister. Like Siobhan, Liam trusts her power to determine if someone was lying or not.
According to an interview behind the scenes, Patrick had been in an acting slump for two years, so it came as a surprise when he was called in for an audition by the casting director.