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Nightmare Fuel: Resident Evil 0
Resident Evil 0 doesn't have the REmake's Crimson Heads, but it makes up for that with a new enemy called a Humanoid Leech (often referred to as "leech zombies"), a swarm of T-Virus leeches that gather together into a human-like form. Aside from being full-blown Demonic Spiders, the things just love to hang around in narrow, claustrophobic hallways, move with a disturbing, boneless walk, and have a reallydisturbingmusical theme. What's more, humanoid leeches can and will make their way into rooms that were previously empty, meaning that you will reenter a "safe" area, only to find as soon as the screen finishes loading that one of these abominations is right in front of you.
The worst part? They look like normal people. The first one you find sits there looking like an old man before his head FALLS ONTO THE FLOOR.
In the Power Plant level, in the same room where you rescue Billy Coen after he took a tumble into the water, you find a stack of skeletons all piled on top of one another with grime on them. These were all of Dr. Marcus's victims after he went mad with testing the T-Virus on humans.
More of an instance of Fridge Horror combined with Tear Jerker, but Rebecca Chambers' last meeting with Enrico Marini, her squad captain becomes a whole lot chilling considering he's murdered only a few hours later by Albert Wesker, his commander and co-patriot whom intentionally sent everybody on this wild goose chase to see how they'd fare against B.O.W.s Her words really hammer in the chilling realization:
"I never saw him again."
Billy, after parting ways with Rebecca, disappears into Raccoon Forest, which is still infested with the zombie dogs. To this day, Capcom hasn't explained what happened to him.
In the kitchen on the back of the train, there is a giant fridge which you can't open. So just walk past it and ignore it. Once you enter the next room and back, a zombie bursts out of the fridge the second you walk past it. A very good (yet likely very predictable if you're familiar with the series) jump scare. Also in the fridge was a bottle of booze, hinting what that person was doing during his last hours hiding from the zombie outbreak.
There's a gas chamber in Marcus's main lab. And it's not well hidden or disguised as something else; it's right out in clear view for people to see. Clearly, this man wasn't below sparing anyone (let alone his colleagues) a terrible death for simply knowing what he was doing.
Most of the files you find in the Research Center are chilling reads as most of them are from attendants of the center and either witnesses or victims of Marcus's cruel research. Most of them are written with the writer fully aware Marcus was on to them.
The Proto-Tyrant (the prototype of the Tyrant from the first game) is the very epitome of body horror. Its lips have deteriorated, there are gaping holes at the sides of its mouth, it violently twitches like it's possessed every ten seconds or so, and to top it all off, its spinal cord is out in complete view. It also came insanely close to cutting Rebecca's last route of escape from the facility with a flick of its claw had she not already have called for the elevator.