Kestrel was the original name of Kettle.
She had black eyes and black hair, but with age, some of it had turned white.
Kestrel of Buck was twin sister to Gull. They were identical. Their father was a fisherman in the Buck Duchy.
Both Kestrel and Gull were Skilled and became members of Stanchion's coterie. Stanchion's coterie worked for Queen Diligence. Besides Kestrel, Gull and Stanchion himself there were two other members.
Kestrel was strongly Skilled, and used the Skill both to alter her body to remain young and heal itself, and to kill. She slew Gull in a jealous rage when she found her in the arms of Stanchion - her lover and the Coterie leader. As punishment, she had her Skill locked within herself and was banished from the Six Duchies over 200 years ago.
Later in life, she used the name Kettle, and travel to the Mountain Kingdom in search of the White Prophet. She ended up helping Verity to complete his stone-dragon.
Long after her death, Lord Golden uses the name Merchant Kestrel for himself at the inn on the Buckkeep side of the river from Newford where Starling keeps watch for the return of Prince Dutiful.