This is from Rick and Morty btw, explanation in comments if you haven't seen this episode

Supernova: He is standing behind a copy of himself, and the copy is watching over the universe. Suddenly, the universe explodes in a fiery explosion as everything he lives for dies. The copy turns into nothing but ashes at the will of the multiverse, for he has failed his job. His one true fear is to let the things he’s worked eons to protect suddenly die.

Phantom: Birds doing really inconvenient things.

*a bird flies down and hits phantom's mask*

Phantom: *grabs the bird and stares him dead in the eye*

(i love how you just ignored the bone-chilling horrifying tale i came up with for Supernova)

(well there wasn't much I could do with that lol)

*An owl flies down, smacks phantom in the back of the head, and hits the ground unconscious*

(lmao)

Phantom: Is this for real?

(he isn’t really scared of the birds since like it’s just like canon at this point he comes back every time he dies somehow but i might as well just)

Gingerbread Man would see general Nox killing his entire family
Montie would see a masked figure burning a pile of pizza

Im not gonna ask about the Pizza

X: Well, Its a bottomless hole, Why not *Jumps in*

*since I don't know anything about X he starts out just in a dark cave surrounded by various shadowy creatures*

X: Heh cool, huh? *Sees something horrifying thing for him*

*several of the creatures start staring at him*

X: The hell are you looking at?

simple since i have plenty of joke characters and normal characters
the normal ones:
colt: nothing as in sheer darkness. no one. nothing. they fear being alone with nothing
bardota: colt
the joke ones: a drawn body as they were all made with irl materials

A man named Jay finds himself in a chilling predicament as he tumbles into a nightmarish hole. As he dusts himself off, he begins to notice something peculiar. His surroundings morph into a dystopian labyrinth, and an eerie revelation strikes him like a thunderbolt: his reality is nothing but a fabrication within a sinister social media platform. Shocked, Jay discovers that he is an 'oc' (original character) in this twisted digital realm.
But there's more to Jay's newfound understanding. As he runs a hand through his hair, he feels a sharp jolt of pain. To his horror, Jay realizes that one of his once magnificent horns has been chipped, serving as a grim reminder of the precarious state of his existence. His entire reality, once vibrant and dynamic, now trembles on the brink of collapse.
With this fractured perception, Jay delves deeper, determined to expose the manipulative machinations at play. Will he find a way to break free from this virtual prison and reclaim his true self? Or will he be forever trapped within the confines of this haunting social media mirage? ( this is not Canaan to the story I will be telling soon)

Wow you just made a whole Story

also the robot ones which i havent mentioned:
1 would get teleported out after an hour or so due to a safety feature to maintain it
and the other is to old so it would shut down in there after a while anyway but it would see the list of warcrimes as it would taunt them for what they had to do in order to survive

The dreams are lightning fast though

For example Morty was only in there for a few seconds from Rick's perspective

its a manual and automatic thing
if an hour passed they would get teleported however if an sos is sent they woild get removed within the second

In the dream it could be several years

In reality it'd be like 10 seconds

a 14 picosecond teleportation would make it like a day type feel so it would be fine as it has no emotions so it would just be stuck in a hole for awhile

Eren: *She jumps downs and sees the god of war, Ares, brutally murdering everyone she loves*

Eren:...

*ares looks at eren with murderous intent in his eyes*

Eren: *the vison of Ares flickers in and out of her best friend, Matt. Despite this, Eren runs away*

Rick and morty is the worst

It's a bit vulgar and weird at times but I don't think it's that bad.

I like it :(

*For traveler, it was nothing but a dark void*

*There were corpses there and here, and they were all Traveler's friends*

*But Infront of him there was Collector's corpse*

*A single tear dropped down his face*

401: Inky hating her
i'd elaborate but the social anxiety is going crazy

Potato: I fear nothing! *he sees something in the darkness* oh no

Eggy: Sees the memories in his head of Omeletta getting executed by EC, Peyton getting brutally murdered by Ultimitum, and Inky sacrificing herself to stop him.

Ove: Always alone, he never manages to get Astra to reciprocate his feelings. She always seems so close yet out of reach.

Essy: refried beans

Hmm

When beldum would jump down, he would see Shi trying to drag him into an underworld that gods are put in, which means that Beldum's greatest fear is death.

To put it simply, the fear hole is a random hole in a Denny's bathroom where people jump in, and are forced to face their greatest fear.

The hole isn't actually that deep, but you go unconscious when you hit the bottom and the actual fear-facing happens in a dream

And the dreams can be VERY crazy

It'll even go as far as to trick you into thinking you've escaped the hole, and lived for several years, only to make you climb out again putting you right back where you started.

This thing can do some SERIOUS sh*t just to scare you

...

Anyway, for the sake of the RP it works on all conscious beings. Humans, robots, spirits, etc. it works as long as they can fear something.