Nostrovite The Nostrovites were a race of shapeshifting humanoid s . Biology . The Nostrovites , in their natural form , appeared to vaguely resemble a human , but with red eye s , sharp claw s and teeth , and visible blood vessels . Nostrovites were carnivore s , but only ate living flesh and would normally ignore corpses . The females , at least , could create a sticky , web - like structure to keep prey alive until they were hungry again . The blood of the Nostrovites was black . Females were apparently a lot tougher than the males ; three bullets from a revolver were sufficient to kill a male Nostrovite , but the female was still on its feet after taking three rounds of bullets to the torso . This was attributed to " some mother instinct or something " by Owen Harper . With the use of their proteus gland s , they could adopt other humanoid forms . Though they could mimic appearances , they could not mimic smells . This allowed Gwen Cooper to identify the real Brenda Williams from the imposter because of Brenda ' s " bloody awful perfume " . ( TV : " Something Borrowed " ) Life cycle . The Nostrovites , like many other species , had two sexes — male and female . However , they also required a third member : a host . After fertilising the female ' s eggs , the male would take the eggs and store them in a sack in his mouth . After finding a potential host , the male would bite them and inject the eggs into the host ' s bloodstream . The eggs would quickly develop inside the host as if the host was merely pregnant with another of its species . After a while , the female would track down the host and tear them open to release the young . This process was Nostrovite childbirth . The newly - born child would then feast upon the corpse as its first meal . ( TV : " Something Borrowed " ) History . The Nostrovites were familiar to Jack Harkness . At some point in their history , some Nostrovites discovered Earth and developed a taste for human flesh . In 2008 , a mated pair of Nostrovites came to Cardiff , presumably through the Cardiff Rift . Though the male was killed by Jack Harkness , it was able to inject Gwen Cooper with egg s by biting her on the arm . The day after the attack was Gwen ' s wedding , which she went through with even though the female was still out there . The female followed her to the wedding and took the form of Carrie . It killed Mervyn and captured Toshiko Sato and Banana Boat . Later when it was discovered , the female took the form of Brenda Williams and tried to hold Mary Cooper hostage , but was shot by Gwen . The Nostrovite survived , and tried to get closer by taking the form of Jack Harkness , but Gwen was able to escape again . Eventually , the Nostrovite eggs were removed by Rhys Williams using the singularity scalpel and the female was destroyed by Jack . ( TV : " Something Borrowed " ) Behind the scenes . Torchwood website . The series 2 version of the Torchwood website had a preliminary investigation into the Nostrovites by Owen Harper . He speculated that the species has many of the hallmarks of a composite race , and could have taken . He observed hooks in the specimen ' s DNA , suggesting the species required a genetic sample to shapeshift . He said that " Even when it ' s in human form , the brains are located in its abdomen . "