Alien Autopsy: Chapter 12, appropriately titled "Autopsy", features the players conducting a experiment, which involves climbing inside a frozen Necromorph called the Nexus and poke its nervous system with electrified harpoons.After completing the mission and riding the same elevator back up, however, Isaac suddenly asks Carver if they're going to check out the place or not, saying they've been standing in the elevator for the past five minutes. Following her will lead Carver and Isaac to an elevator where Carver will begin to feel effects from a Marker. All Just a Dream: In the second co-op mission available during Chapter 11, Carver will see a hallucination of a dead woman walking back to an earlier part of Chapter 10.It's the planet being torn to pieces behind you by The Moon. Advancing Wall of Doom: In the final level.Revealed to be true in the Liberation novel, where they were turned into Necromorphs. His Marker hallucinations even take the form of a toy soldier his wife gave his son the day of the outbreak. After the Marker was exposed, an outbreak of Necromorphs erupts and he cannot contact his wife and child, both of whom are completely vulnerable. Adult Fear: Definitely in Carver's case.Plus, many of the psychological horror elements are restricted to Co-Op missions and happen to Carver instead of Isaac. Also, Necromorph enemies are a lot faster and are much harder to hitstun, so you'd better learn to use that dodge roll. Actionized Sequel: Adds new mechanics such as dodge rolls, crouching behind cover and Third-Person Shooter segments against enemies with guns.At worst it would've left players completely defenseless in case they happened to carry nothing but "wrong" weapon types at this moment. Justified, since coding physically sound restrictions for what barely amounts to two minutes of gameplay would hardly be worth it, especially since most players probably won't even notice.
The sequence uses the game's space walk mechanics (no air, no gravity), but despite floating in gastric juices instead of vacuum, Isaac's weaponry including missile launchers and everything based on electricity works just the same as it does in space or under regular atmospheric conditions.
Abandoned Mine: Upon first landing on Tau Volantis, you have to work your way through a snowy mining facility overrun centuries ago by the Necromorphs.