EVA first appeared in Metal Gear Solid 3: Snake Eater as Naked Snake's informant in Volgin's ranks. She dissappeared for a large amount of time in the story as she did not feature in any of the other Metal Gear games. However, she recently featured in Metal Gear Solid 4: Guns of the Patriots as Big Mama.
 Metal Gear Solid 3: Snake Eater
In this game, EVA was first introduced as an NSA codebreaker who had defected to the Soviet Union in 1960. She was supposedly working as a spy for the KGB as Tatyana, Sokolov's wife. The player was expecting to meet ADAM but EVA said that he couldn't make it. Throughout the game, she helped Snake out more and more and their relationship grew stronger. Near the end of the game, Volgin found out that Tatyana was actually a spy because she had been snooping around in an underground vault with the microfilm containing all of the data on The Philosopher's Legacy. Other evidence included the fact that she was carrying a radio with her, and that she smelt strongly of petrol, which Ocelot recognised from seeing EVA on a motorbike earlier in the game. When EVA and Naked Snake eventually escape at the game's finale, they are shown sleeping together. When Snake wakes up, he finds EVA to have dissappeared. She took the microfilm that The Boss gave her, and she left a recording for him to listen to. Amongst other things, it revealed that EVA was double-crossing the KGB and was actually working for The People's Republic of China. Her mission all along had been to retrieve The Philosopher's Legacy, and return with it to China. However, after the credits have rolled, Ocelot revealed that the microfilm that EVA got was actually a fake, and the real one had been returned to America.
 Metal Gear Solid 4: Guns of the Patriots
In this game, EVA is known as Big Mama, the leader of a resistance group in Eastern Europe. She is in charge of hiding the pyx of Big Boss the legendary soldier who was known as Naked Snake in Metal Gear Solid 3: Snake Eater. She reveals that she was the surrogate mother of twins Solid Snake and Liquid and had always felt like a mother to them. She tells Snake that when she returned to China and they found out that the microfilm she acquired was a fake, she was kicked out. She met Big Boss again in 1968 in Vietnam, where he asked her to join The Patriots, a new group founded by Major Zero. She agreed and was then one of the only survivors left from the original group. After Liquid sets fire to the boat where Big Boss's pyx is being kept, Big Mama turns hysterical and tries to save the body. Solid Snake tries to pull her to safety but it is too late, she dies in his arms.
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