Fiona starts off the game with amnesia, in a cage, surrounded by instruments clearly used for torture and butchering, and wearing nothing more than a sheet.
"Endless Zero"'s lyrics seem to imply Ayla wanted Fiona's Azoth for herself.
Each of the stalkers fits this trope in some form.
Debilitas is three times the size of Fiona and can’t speak very coherently, reducing his mindset to that of an infant. Many players seem to find his antics funny until he knocks Fiona over, whereupon he can pound her body to a pulp or pick her up in a bear hug, which breaks her back.
Daniella is considered to be one of the most disturbing characters in horror gaming, and for good reason. There are many things that are wrong with the seemingly emotionless maid, ranging from her fixation and jealousy of Fiona, her unpredictable and unstable outbursts of mania, and her twisted belief that she is merely a homunculus in the guise of a beautiful woman that can never be "complete" unless she takes out the source of Fiona's Azoth: her uterus. What makes her unique among the stalkers is that Daniella is capable of switching back to "normal" at random - Fiona can stumble across the maid cleaning in various parts of the castle as if nothing had ever happened. It may seem as if all is well, but Daniella will inevitably resume the chase when you least expect it.
Her introduction as the second stalker has Daniella forcing Fiona into having dinner and then inappropriately touching her as the younger woman sleeps on the guest bed afterwards. Upon causing her to wake up in a panic, Daniella walks away muttering "I am not complete," before violently banging her head against a window until it breaks. She then takes a large shard of glass as her weapon and proceeds to hunt down Fiona.
If Daniella spots Fiona, she may point and hiss at her.
Riccardo wants Fiona to birth him a clone of himself ("LET ME INTO YOUR WOMB!"), and then it turns out he's a clone of her father. Let the implications sink in.
Lorenzo is a dirty old man (technically Fiona's grandfather) who can't walk, but get him on his hands and he becomes the fastest character in the whole game. Then he regains his youthful appearance, has instant-kill attacks, and can teleport right in front of Fiona.
The music in the game, while sparse, is chilling in its own right. Then you realize that the music has stopped, and one of your pursuers is on the other side of the door you were about to open. Many first-time players likely experienced severe fright because of how the game uses its music. When Fiona is hiding and the stalker leaves the room for a bit, the game will give a "Coast is Clear" message. This seems like an okay to leave the hiding spot, and sometimes it is... but, more often than not, the stalker's theme will pick up again, and chances are they will reenter the room before the player understands it was a false alarm. These precious few seconds will be enough for the stalker to return, preventing Fiona from hiding again and possibly even giving away the hiding spot entirely. The player needs to wait for the normal ambient music to resume in order to guarantee that the stalker has given up.
Examine the figure sitting on the couch in the Old Mansion - it's a mummy. If you leave the room and then go back to it, the mummy will be in a different position.
A room in the Old Mansion houses a massive mammoth that appears to have barged through a wall and died upon impact with its eyes wide open. If you walk past it while taking a closer look at its eyes, you can see the mammoth's pupils following Fiona. It's no wonder Hewie always gets uneasy in this room.
The strange hand that comes out of the crypt in the graveyard. While Fiona will note that it doesn't seem malicious, it's still creepy as hell and can catch you completely off guard. Things get even more horrifying when you give the hand a white mandragora and hear it being eaten alive as it screeches in agony. When it's done, you can then hear something shuffling away... Kinda makes you not want to go down there after all.
There are two cutscenes that the player can receive after playing through the game once. The first is before the Riccardo battle, where an unconscious Fiona is being given an ovulation test by him after he's obviously stripped her down and redressed her (in a dirty gown, mind you). The second is immediately after the same battle, where Lorenzo crawls to Riccardo's body and sucks his Azoth out.
If you go into the kitchen near the beginning of the game, you can trigger a cutscene where Fiona watches as Daniella stirs a pot. When she lifts the ladle, a red liquid drips down from it... along with what appears to be blonde hair. Go back to the kitchen later on when Daniella isn't in there and examine the pot; Fiona herself will say that it looks disturbingly like human hair. She is later forced into having dinner by Daniella and feels sick afterwards. Remember Fiona's mother? Yeah, the implicationsaren't pleasant.
In the Old Mansion during Daniella's chapter, Fiona comes across a room with a carousel inside. When you return to it later after moving some rooms around, it's become bloody and rusty. The formerly cheery carousel music is also grossly distorted now, making the whole thing that much more disturbing.
The corpse in the torture room, which is apparently still alive. Go on, try to take the key from it before solving the puzzle.
Panic Mode. You have little control over Fiona as she runs around tripping and slamming into walls. There's a good chance that she'll also fall over and remain helpless on the ground for an extended period of time. The creepy voices in the background repeatedly saying "Fiona" don't help. And did I mention that the screen goes black and white?
The various ambient and chase themes are creepy or pants-crappingly scary for similar reasons, perhaps even more so given the chase themes' tendency to speed up or slow down based upon how close to or far away from you the stalker happens to be at the time. Here are the four main sets:
The failed homunculi scattered throughout the castle.
They are naked, deathly pale, and basically braindead. All of them remain stationary and merely repeat a random action, ranging from mumbling incoherently to licking the floor.
There are also the baby homunculi, which Fiona accurately describes as looking like "fatty clumps of meat." The very first time you encounter one is particularly unnerving: You round a corner to see it in a dimly lit alcove, just... standing there, waiting. Upon seeing Fiona, they squeak and run at her; if they manage to catch her, they hold onto her legs, rendering her immobile, and let out a continuous, high-pitched screech. You'd better be fast in either kicking or having Hewie deal with them.
One room has several of them suspended in tanks, seemingly dead. If the player examines them and then goes to leave the room, the sound of shattering glass will be heard as one of the homunculi breaks free of its tank.
It is possible to come across one being cooked - and then it suddenly screams, revealing it's still alive. A disgusted Fiona will comment that the more she looks, the more it resembles a child.
Each stalker seems to represent a distinct and dark aspect of rape or human sexuality and how various instincts and urges can turn people into monsters, desperate victims, or both. They all desperately want something from Fiona physically.
Debilitas obviously represents innocence in that he does not know that his actions are hurtful to others. He lacks the intelligence to understand and resist his powerful "urges." If he catches Fiona, he will attempt to play with her, which, given his massive strength and innate aggression, results in him killing her. The most common death at Debilitas' hand is a bear hug. If Fiona doesn't break out of it or Hewie doesn't stop him, Debilitas snaps her spine.
Daniella represents sexual jealousy and repression. She also acts out of physical (and quite possibly sexual) abuse at the hands of Riccardo. She is so desperate to become a real human woman that she attempts to rip Fiona's uterus (which houses her Azoth) out of her in an extremely brutal and gory way.
Riccardo does not see Fiona as an actual human, but rather a vessel meant to give birth to him. His intentions towards Fiona are arguably the most sexual in nature of all the stalkers. Additionally, of the three stalkers who want the Azoth, he is the only one who doesn't want to take it from Fiona; rather, he wants to claim it, much like the notion of claiming someone's virginity or innocence.
Lorenzo's motives are quite similar to Riccardo's, although he seems to place a particular emphasis on gaining power. He intends to hunt down a very non-consenting girl and forcibly take her Azoth for himself. Similarly, a rapist often does not rape for physical pleasure, but because sexual assault is physically and emotionally devastating for the victim while it gives the rapist a great degree of power.
The various kill animations from all the stalkers are terrifying.
Debilitas seizes Fiona in a bear hug and snaps her spine if she fails to escape. He also has a rare chance of dropping on top of Fiona and breaking her neck.
Daniella grabs Fiona by the arm and starts laughing maniacally as she tries to escape. Should Fiona fail, she impales her on her weapon. She can also pounce on Fiona and slit her throat.
Riccardo shoots Fiona dead, which may be preceded by him slapping her to the ground if he's close enough. He can also simply lift her by the neck and choke her or repeatedly slam her head into the ground.
Old Lorenzo grabs Fiona's leg and tries to pull her to the floor. If he succeeds, he races over to her and slams his palm onto her uterus, doing something that causes her to violently convulse and die.
Young Lorenzo grabs Fiona from behind and holds her close. Should Fiona fail to escape, he plunges his magic-coated hand into her uterus, instantly killing her.
Debilitas plays with Fiona's body like a child with a new toy, possibly tearing her limbs off in the process.
Daniella moans and laughs hysterically as she cuts out Fiona's uterus.
Riccardo whispers "Yes, Azoth..." as fabric is heard being shifted around, shortly followed by him moaning in ecstasy.
Old Lorenzo hacks and slurps noisily as he drinks Fiona's Azoth.
Young Lorenzo does the same as the above except with a triumphant laugh and some grotesque tearing noises.
Flaming Lorenzo yells "Azoth! Eternal life!" and cackles with anguished laughter as we hear his flesh being melted away by molten fire.
If the stalkers trying to kill Fiona wasn't enough, the castle itself has a number of traps and dangerous rooms that will also kill her should she carelessly traverse them:
The Red Marionette room is decorated with countless eyes on one wall that will shoot needles at Fiona should she try to just walk by it instead of deactivating the trap.
A dimly lit room found right before Debilitas' boss fight is filled with spiked pits and has a near-invisible path that only Hewie can detect. One wrong step and Fiona is screwed.
There is a Truth and Lies room where examining the wrong object will lock Fiona inside and unleash a swarm of flesh-eating bugs.
An iron maiden serves as an unlikely and unreliable hiding spot for the player to use in the torture room... Should Fiona be caught hiding inside it by Daniella, she'll calmly lock her in and activate the trap.
One corridor has a suit of armor wielding a crossbow at the end of a series of tiles, where stepping on the wrong tiles three times will result in the suit of armor shooting an arrow at Fiona.
Perhaps the most gruesome, the rock crusher can potentially kill Fiona should she step onto the conveyor belt while it's turned on. Not only does she get flattened to paste off-screen, but you also get to hear the grisly noises and see her blood afterwards. This is easy to do accidentally on your first playthrough, as you could realize that you need to lure Lorenzo to the conveyor belt, but wrongly surmise that you have to step on it yourself to do so.
And finally, Ending D. The way to obtain this ending is to mistreat Hewie throughout the game until the Riccardo chase sequence in the forest. As a result of Fiona being abusive to Hewie, it's implied he either dies from Riccardo's gunshot wound or abandons Fiona out of spite. Fiona wakes up days later in a small glass box in a dimly lit lab, where Riccardo announces he will rape her to birth himself an immortal body. As a smiling Riccardo marches to the box, the camera abruptly pans out to a seizure-inducing sequence of Fiona screaming in complete terror before the screen fades to black. The ensuing epilogue sees Riccardo made good on his taunts, as Fiona is now heavily pregnant and goes completely mad from the revelation she was raped and impregnated by her technical uncle with a clone of himself.
The implications of this ending become far worse when the game hints Riccardo is a fairly mediocre alchemist, having many failures to his name like Debilitas and the braindead homunculi loose in the estate. We don't know if his plot to rebirth himself will even be successful, and moreover, what he plans to do to Fiona if it fails, given his track record as a violent misogynist.
(ambient) and Innocent Freak