Carrie (Something Borrowed)

"Carrie" was a female Nostrovite. She was the mother of another Nostrovite's child, who implanted an egg into Gwen Cooper to incubate it. She disguised herself as a guest at the wedding of Gwen and Rhys Williams to forcibly take her child. Her "mother instinct or something" made her unstoppable after taking several bullets to her stomach. Rhys destroyed the child with the singularity scalpel and "Carrie" was killed by Captain Jack Harkness. (TW: Something Borrowed)