Alaya

Alaya was a female Silurian warrior from a vast underground city that was disturbed by a welsh mining facility in the year 2020. She came to the surface and took people as hostages. (DW: The Hungry Earth)

History
Alaya came to the surface and took Elliot under the ground, also possibly Amy Pond and another person under ground to be kept as hostage. The Doctor sprayed her with a Carbon Dioxide fire extinguisher and Rory bundled her into the back of a van. She was then put into the crypt of the church where she said one of them would kill her and she knew which one, but never revealed the one.