Belladonna is one of the Kuja of Amazon Lily, persumably the doctor of the island. She is the one who set Luffy on fire to get rid of the roots of the mushrooms he ate. . She also reveal to Luffy that Marguerite was the one to save him when the others amazons were preparing to shoot him. She is later seen by Boa Hancock's side after she suffers from a mysterious disease.

(Source: One Piece Wiki)