Parasite Eve

Parasite Eve is a multimedia franchise created by Hideaki Sena and Square Enix. The series supposes that mitochondria, which have their own DNA, are actually a single conscious organisim that has been waiting for an opprotunity to take over all mitochondria-dependant life on Earth. This organism, Eve, makes her first attempt to give birth to a pure mitochondria life from in Japan, but ultimately fails when the mitochondria of the father's sperm rebel. She makes another attempt in New York City, and is more successful due to artificial sperm, but the new lifeform is defeated by the similarly enhanced mitochondria of Aya Brea. After that, mitochondria mutants become more or less a pest problem.

Aya Brea
Aya Brea is a former NYC cop and governemnt agent tasked with dealing with mitochondria-mutated creatures. She recieved her mitochondrial powers through an eyeball that was transfered from her twin sister Maya, who herself had recieved a liver from Eve's original host in Japan. Unlike the various hosts of Eve, Aya's mitochondria mutated to resist Eve's power, while still giving Aya magic-like abilities. One of these abilities, the last ability to be learned in Parasite Eve, and used in a cutscene to save herself from Golem No.9 in Parasite Eve II, is Liberate, which transforms Aya into a blue winged angel that automatically attacks nearby enemies with her fists.

Eve
Eve is a conscious manifestation of mitochondria who plans on replacing all eukaryotic life with mitochondria. She even claims to have manipulated all life for the purpose of creating a world, modern society, which is easiest for mitochondria to take over. She can control the minds of people, mutate the body of her host, break herself and other organisms down into sentient puddles of mitochondria, and control the mitochondria of other life forms. In humans this usually results in the mitochondria over-reacting and causing the person to spontaneously combust, while in animals the mitochondria are free to reshape the animal into a monster.

Eve first attempts to put her plans into motion in Japan. There she has manipulated a genetic scientist and a woman, Kiyomi, to fall in love, as well as causing renal failure in another girl. She then kills the woman, knowing that the scientist will attempt to cultivate his wife's mitochondria. As an organ donor his wife's kidneys are donated to the girl, and soon become a source of nightmares and pain. Meanwhile the scientist's cultivation bears fruit, allowing Eve to create a physical body out of the liquid mass of mitochondria. She "takes" the scientist's sperm with the intention of impregnating the mutating girl and creating a new Ultimate Lifeform to take over the world. After finding out about Eve's manipulation the scientist is devistated, but is still convinced that the love he had with Kiyomi was legitimate. He confronts Eve, and it seems as if the body Eve had created was truely Kiyomi as well. They embrace as the scientist's mitochondria ignite and incinerate them both. The Ultimate Being ends up dying before conception due to a revolt by the sperm's mitochondria.

In the events of the video game Eve later reappears in New York. For unknown reasons she remanifests in the mitochondria of Maya Brea, sister of Aya Brea. Maya died in a car crash years beforehand, but her liver was transplanted into another young girl, Mellissa Pierce. The immunosupressants Melissa took eventually allowed Eve to regain control, and begin a widescale attack against all New York. As Aya investigates she discovers a scientist working with her, helping Eve to bring about a mitochondrial revolution and providing her with synthetic sperm that will allow her to give birth to the Ultimate Being. Ultimately she is successful, though both herself and the Ultimate Being are killed by Aya.

She makes another half-hearted attempt to take over the body of Eve in Parasite Eve II, a clone of Aya grown specifically to be a host, but is stopped before being able to do much of anything.

Neo Mitochondria Creature
After Eve's defeat in New York City mitochondria mutations spread throughout the Americas, reproducing and mutating further. Tests by a secret organization were run on these NMCs, and a method was developed that could create an NMC which could mimic a human, enter a populated area, and then transform.