Nagaina is Nag’s wife, and one of the bloodthirsty snakes that Rikki-tikki encounters. Readers first meet Nagaina shortly after Rikki-tikki enters the bungalow garden. The two cobras resent the British family who own the estate, and they are enraged that they have welcomed a mongoose into their home, given the snake-killing abilities mongooses famously possess. Convinced that Rikki-tikki will harm their eggs, Nagaina and her husband try to kill him. Nag pretends to converse with Rikki-tikki so that Nagaina can sneak up behind him, but their plan is foiled by Darzee at the last moment. After Rikki-tikki kills Nag, Nagaina tries to kill him and his new adopted family for the second time, but Rikki-tikki ultimately defeats Nagaina after battling with her in the cobra’s underground lair.
Nagaina and her husband are clearly the story’s antagonists. However, Nagaina is characterized as being a slightly more sympathetic character than her husband. Nag is purely evil, and his attacks on Rikki-tikki and Teddy’s family highlight his cruel nature. However, while Nagaina also attacks Rikki-tikki and his adopted family, she does so to avenge her murdered husband and to protect the lives of her unhatched children. One gets the sense that Nagaina’s family is her first priority. For instance, she instantly abandons her pursuit of Teddy when she realizes that Rikki-tikki has her last surviving egg. She continues to prioritize her family by grabbing the egg and attempting to retreat into the safety of her cobra hole instead of fighting Rikki-tikki. As a result, one might compare to the story’s other mothers such as Alice and Darzee’s wife, who would clearly do anything to protect their children.