A female Silurian warrior who shares a house with Jenny Flint, her maid and eventual wife, in Victorian London. She owes the Doctor a debt after he convinces her not to seek retribution when some of her people are killed. She later becomes a consultant for Scotland Yard, and investigates the crimes of Jack the Ripper. She is summoned by the Eleventh Doctor to help rescue Amy Pond and her baby from Demons Run. Enjoys drinking human blood as if it's wine, but is generally not a threat to humans.