The spacehulk psudo-horror scenario I keep meaning to use is something like the imp from the Star Wolf series of books.
Basically a small, intelligent saboteur who work in subtle ways for a while. Often this can look like a haunting, especially on the spooky ghost ship the PCs just walked onto.
In HARP I might use something like this as the "imp".
Asset #7 - Madji Belter Spy (5)
EP: +66 PEP: -9 Init: +15 DB: +50 BMR: 2.8
RR Bonuses: Stamina +50 Will +42 Magic +5 Electronic -5
St: 50 0 SD: 66 +6
Co: 65 +5 Qu: 61 +5
Ag: 86 +10 Re: 86 +8
In: 86 +10 Pr: 50 0
Weapon Skills:
MR: 1HEn (Minilaser) +45
Martial Arts Strikes +45
Demolitions +70
Armor: Ballistic + Spacesuit
Talents: Spy Level Bonus, Extra Limbs, Motion Sensing, Radiation Resistance (minor), Manual Dexterity
Key Skills: Acrobatics (2) +26, Climbing (1) +15, Contortions (5) +41, Demolitions (12) +70, Martial Arts Strikes (7) +45, MR: 1HEn (Minilaser) (7) +45, Appraisal: General (1) +23, Computer Operation (9) +63, First Aid (2) +28, Language: Racial (S) (6) +48, Language: Racial (W) (6) +48, Language: Other Racial (S) (4) +38, Language: Other Racial (W) (3) +33, Machine Op: Tools (8 ) +58, Lore: Own Culture (1) +21, Lore: Cosmography (6) +46, Perception (6) +46, Resistance: Stamina (5) +50, Resistance: Will (5) +42, Signaling:Sensors and Countermeasures (7) +53, Vocation: Crewmember (2) +26, Duping (3) +25, Interrogation (1) +15, Armor Skills (4) +30, Endurance (5) +66, Jumping (1) +15, Swimming (1) +15, Zero-G Maneuvering (10) +66, Chemistry (1) +23, Xenology (1) +23, Ambush (4) +36, Camouflage (3) +35, Computer Hacking (12) +82, Electronic Bypass (10) +68, Forensics (1) +21, Locks & Traps (9) +75, Stalking & Hiding (13) +82, Poisoning (3) +31, Sniping (2) +26, Streetwise (1) +15, Trickery (2) +26, Computer Programming (2) +28, Civil/Habitat Engineering (1) +23, Power Engineering (6) +48, Transport Engineering (7) +53, Space Pilot: Starship (1) +25
Resistance: Magic (0) 5, Stamina (5) 50, Will (5) 42, Electronic (0) -5
Languages: Racial (S6/W6): 48/48, Other Racial (S4/W3): 38/33
Asset #7 was a young child when his family was captured by raiders. The rest of his family was killed, but the raiders kept #7 as a slave. After several years of menial cleaning and serving #7 was transfered to another location. Here he was conditioned and trained for over a decade. #7 was taught to hide and evade capture, to set traps, and harrass shipboard crews. #7 was also trained to hack computer systems and broadcast sensitive data to his masters. His final training included explosives training and enineering for critical shipboard power and structural systems.
Asset #7 was made into a recoverable but ultimately expendible sabatour intended to compromise and cripple any ship he was released on. He hides in little used service areas, then works to kill or incapacitate the crew while disabling the ship. He signals his masters to then come retrieve both the prize and himself.
#7 remembers little of his free youth, but perhaps he could be convinced to give up his master's mission, or perhaps not.
Best Regards,