The gatherer enemies are deformed human-like monsters; their eyelids are cut off and their bottom jaw is mutilated and stretched down and attached to their chests leaving their mouths permanently open.
Both BioShock and BioShock 2 consist of enemies called Splicers, who were once normal humans that were heavily mutated and driven insane from a drug called ADAM, which they used to re-write their genetic codes to develop "psychic" powers such as telekinesis and pyrokinesis. The game also contains the iconic Big Daddy, which is a man whose skin has been removed, and whose organs have been grafted to the inside of a modified deep-sea diving suit. BioShock Infinite uses a similar premise, although in this case series of compounds called Vigors grant the player extraordinary abilities; however, unlike ADAM they are consumed orally rather than injected. In this game, the Big Daddy has been replaced by the Handyman, a human whose spinal cord, head, and heart have been connected to a steampunk robotic frame with minor effects like psychological trauma.
A pharmaceutical company uses a mutagenic T-Virus in order to produce monsters to sell as weapons. The most basic infected were Zombie versions of whatever was infected or giant versions of insects, however, human/insect and human/reptilian hybrids, malformed super-soldier projects called "Tyrants", and various other creatures exist. Later games introduce more viruses and las plagas (an ancient parasite which take over animal nervous systems), which feature more variations of monsters.
The Squaresoft (now known as Square Enix) video game based on the 1996 Japanese Science fiction horror novel of the same title, was released in 1998. The premise of both the novel and "cinematic RPG" being that the mitochondria, organelles from early aerobic bacteria that formed a symbiotic partnership with cells of most present day multicellular eukaryotes, e.g. humans, are able to retain their separate identity as independent organisms in the form of cellular parasites. A dispersed intelligence, known as Eve, was able to take over the consciousness of certain individuals to make them reproduce and form an ultimate organism that will bring the downfall of humanity and other creatures alike.
Based on the 1982 movie "The Thing" you play as Captain Blake, a member of a U.S. Special Forces team sent to the Antarctic outpost featured in the film to determine what has happened to the research team. The enemies come in three main varieties. "Scuttlers" are small Things formed from the limbs and appendages of infected personnel. "Walkers" are larger than scuttlers, and much stronger and finally, the Bosses are larger and much more powerful than Walkers.
The basis of Phyrexia, an antagonist faction composed of assimilatory biomechanical undead. The Scars of Mirrodin block in particular focuses on this theme, in which assimilation and infection are emphasised upon, and Phyrexia has branched into all colours of mana, introducing new forms of mutilation.
In the Shadows Over Innistrad block, the gothic horror inspired setting of Innistrad undergoes a transformation; at first marked by subtle mutations in both the human and the already-monstrous living residents, it gruesomely distorts many of the plane's inhabitants in the image of the invading cosmic being, Emrakul.