Vastra

Vastra was a female Silurian warrior who was friends with a human woman, Jenny in Victorian London.

She was one of many people who owed the Doctor a debt: she awoke during the construction of part of the London Underground and wanted to avenge her deceased people on the workers, but the Doctor convinced her not to give in to rage. Vastra would instead make a home in London, disguising her Silurian form to most people and acting as a freelance adventuress.

After eliminating Jack the Ripper, she was summoned by him to help in the mission to rescue Amy and her baby at Demon's Run. She and Jenny arrived at Demon's Run along with a army of Silurian soldiers, they both survived the battle with the Headless monks. She also knew a lot about Time Lords as she refers to regeneration, the Untempered Schism and the time vortex. (DW: A Good Man Goes to War)