Cerys an Craite (also called Sparrowhawk) is the daughter of Crach an Craite and the sister of Hjalmar. In The Witcher 3: Wild Hunt, Geralt can help either Hjalmar or Cerys to become the new king/queen of Skellige during a quest line.
The young woman is a courageous islander like her father and also has inherited all his stubbornness. She is very self-confident and always up to prove that she can fulfill any task as well as any man.
She embarks on the quest Possession, and sails to Spikeroog to free Jarl Udalryk from a curse to demonstrate her worthiness as ruler.
She is also a possible ally uring the quest Brothers in Arms: Skellige, if her brother Hjalmar becomes king, otherwise, she becomes queen and Hjalmar, the ally.
If she becomes queen, Skellige prospers peacefully under her guidance.