She pretends to be the leader of the guild, when in fact the leader is Illyria. She is North's wife. She has a close relationship with North's younger sister, Illyria. Sierra is known as the "Knight of Thorns". She became a knight in her childhood. Her marriage to North is an arranged marriage. She is ruthless and cold-blooded, and is suspicious of everyone except her family members. She is ready to kill anyone who will be suspicious for her. Ready to kill everyone on the orders of Illyria.