Problem 

It's game night. You were planning on running a Sci-Fi horror game, but haven't been able to prep until now. 

You quickly pull up tools to design and furnish a quick space station themed dungeon crawl, but now need to stock it w/ some appropriate enemies and hazards to actually threaten the players.

(A) Solution

 If you think about it, a ghost is essentially a 2-for-1 deal in terms of encounter design. Their humanoid variants can be your standard stalker enemy that constantly pressure the PCs. Additionally, they could be more of an environmental hazard ala a poltergeist.

 If only there was some way we could tie together Ghosts and Sci-fi in a way the Hard-Sci nerds at the table could tolerate...

Running Psychic Ghosts

 A Malicious Ghost using ESP

Procedure

Exposition

Ghosts are not a supernatural phenomenon, but a consequence of Psychics and Quantum Entanglement. In the beginning, all of what was and ever will be had been contained to a single point. After the Big Bang, all of space and time remain connected through infinitely thin "strings".

 

The (true) first psychics emerged shortly after the invention of FTL engines. Early ship designs were not properly shielded against radiation, let alone the occasional "string" cutting through unsuspecting crew.

 Those that survived being "sliced" were able to manipulate these "strings," influencing their local reality in strange ways. However, upon death, their consciousness was still tied to these "strings," and thus scattered across time as their neurons fired one last time.

 Thus, Ghosts were born. 

Encounters

Due to quantum mechanics, a Ghost is simultaneously everywhere and nowhere at every point in time. Thus, every time you enter an odd numbered room, roll 2 dice (range d4 - d12).

 

On evens, the Ghost is in the box. Use the result as a standard reaction roll, however:

• One die is the Ghost's overall opinion of the PCs. It starts at d6, and raises/lowers by at most 1 die size after a positive/negative interaction w/ the party.
• The other die is the Ghost's lucidity. It starts at d12, and lowers 1 die size if the face is 1-2.

 On odds, the Ghost is not in the room, but still haunts it as a poltergeist. The room is affected as by the first unused option under the appropriate Room Effects list.

Tip: Make this roll beforehand so you can properly foreshadow any danger.

Effects & Extra Abilities

All Ghosts are utilize ESP to see the space-time strings (sometimes dubbed "auras") radiating from all organic creatures. Additionally, Ghosts can use basic telepathy to communicate with any creature that has a brain.

Additionally, each Ghost has a list of Room Effects and Extra Abilities, depending on their Psychic Powers in life. Once the final Room Effect is known, the Ghost can use a Room Effect during when encounter.

ESP (Extra-Sensory Perception)

Abilities: Read minds, project full sensory illusions, and nullifying one of the 5 sense (Disadvantage on appropriate saves).

Signposting: "You smell an old family recipe. Color briefly inverts as you open the door. You swear you heard someone laughing. Etc."

Encounter	Room Effect
1	The taste of bitter almonds dance on the PC's tongue.
2	PCs practically choke on the smell of rotting corpses.
3	Light is still visible, but not emissive. Even night vision is useless.
4	All thoughts are drowned out by someone else's screams.
5	Phantom needles prick PCs skull. Will save to take Minor | Moderate psychic harm when resting.
+6	All of the Above, and leaving the room has a 50% chance of ending up somewhere else.

Telekinesis

Abilities: Push, pull, lift, spin, squash and stretch objects w/out lifting a finger. 

Signposting: "The door is inexplicably harder to push open. Objects seemed magnetized to the door. Some force is pushing against you. Etc."

Encounter	Room Effect
1	Everything in the room feels slightly lighter/heaver (d2).
2	PC's Sense of Equilibrium is unbalanced. Disadvantage on Dex saves.
3	Unanchored objects in the room float aimlessly.
4	Everything in the room has no gravity.
5	Anything not nailed down is flung about as if in a typhoon.
+6	All of the above, and the sinews in the PCs pull apart. Minor Harm, on death they explode into a bloody mist.

Pyrokinesis

Abilities: Control & ignite flames (Minor | Moderate Harm), thermal vision.

Signposting: "You hear sizzling from the other side of the door. The handle is almost white hot. Heat emanates from the gaps in the door. Etc."

Encounter	Room Effect
1	The room is blisteringly hot.
2	The floor is inexplicably coated in oil.
3	Exposed water quickly evaporates.
4	All metallic objects in the room is super-heated (Minor Harm)
5	Anything flammable is set ablaze.
+6	All of the above, and anything cold gives freezer burns (Minor | Moderate Harm).

Pre/Postcognition

Abilities: Roll a die. At any point you may swap any roll made for that die's value. Afterwards, reroll the die.

Signposting: Have an NPC repeat something they just said. Describe what the PC see's while opening a door, and then ask if they are going to open the door. etc.

Encounter	Room Effect
1	Each PC sees an exact copy their childhood room.
2	Each PC has a brief omen flash in their mind. Once describe, it *will* come to pass.
3	Each PC lists a person they've wronged the most. If this effect happens again, one of said people are always in the room.
4	Each PC states a future their character hopes for. That image dissolves from their memory, and can never actually happen.
5	Any failed here roll halves your *expected* lifespan. Con save to avoid a heart attack if needed.
+6	All of the Above, and each player loses a memory when resting here.

Exorcism

It's possible to fight off a Ghost if there's another psychic in the group, but the Ghost and it's influence will reform after d4 rooms.

To permanently deal with the Ghost, you must completely destroy the psychically preserved remains, somehow contain the spirit, or solve their Baggage:

1	Vengeance: They will not rest until justice is finally served.
2	Regret: They will finally rest when they fulfill their promise.
3	Love: They will finally let go once the one they cherish is safe.
4	All metallic objects in the room is super-heated (Minor Harm).
5	Hubris: They will pass on when shown "immortality" has a price.
6	Bound: They will escape once their captor(s) are dealt with.