Vastra

Vastra was a female Silurian warrior who shared a house with a human woman, Jenny in Victorian London. It is implied from dialogue between the two that they shared a both romantic and sexual relationship.

She was one of many people who owed the Doctor a debt: she had awoken during the construction of part of the London Underground and had wanted to take revenge on the workers for the deaths of her "sisters"; the Doctor convinced her not to give in to rage. Vastra instead made a home in London, disguising her Silurian form to most people and acting as a freelance adventuress.

After eating Jack the Ripper, she was summoned by the Doctor 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 an army of Silurian soldiers. They both survived the battle with the Headless monks. It is implied she had known the Doctor for some time as she referred to him as an old friend. The Doctor also informed her about Time Lords as she referred to regeneration, the Untempered Schism and the time vortex. (DW: A Good Man Goes to War)

Personality
Vastra appeared to know the Doctor very well, referring to him as an old friend. She was also quite knowledgeable about the Time Lords, knowing about their ability to regenerate. She also had knowledge of the Untempered Schism and the Time Vortex which showed a considerable knowledge of time itself. Vastra suspected that the reason Melody Pond was part Time Lady was because she had been concieved in the TARDIS while it was travelling through the Time Vortex.

Vastra enjoyed eating humans, but strangely it is implied that she had a romantic relationship with Jenny, despite their species differences and them both being of the same gender. Vastra also didn't eat the two men she and Jenny threatened during their mission to save Amy and her baby (though she did poison one of them with her venom but this was to stop him from calling for help) and apparently the Doctor had once helped her control her rage when her "sisters" were killed by humans. Vastra was a fierce warrior who wielded two swords in combat and held her own extremely well against a group of Headless monks surviving without any apparent injury. She was also very loyal and protective, ordering her allies to protect Melody Pond at all costs.