"Ghosts" Without Magic?

[Cyphr]

- free floating apparitions

As others suggested grav bots. If YTU allows cyberswarms of microbots that were originally used as fancy high tech garden lights.

- hot and cold spots

Neural stunners that are modified to simulated temperature differences.

- locations where characters feel unnatural senses of apprehension, if not outright fear, or other out-of-control emotional states such as anger, lust and so on

natural or synthetic pheromones released in the area by the old landowner trying to sabotage the construction project.

 

[Lord High Munchkin]

- free floating apparitions

As others suggested grav bots. If YTU allows cyberswarms of microbots that were originally used as fancy high tech garden lights.

Or micro-workbots with tiny work-lights... perhaps for cleaning hard to reach places like down sewers and piping.

- hot and cold spots

Neural stunners that are modified to simulated temperature differences.

Dodgy environmental control?

- locations where characters feel unnatural senses of apprehension, if not outright fear, or other out-of-control emotional states such as anger, lust and so on

natural or synthetic pheromones released in the area by the old landowner trying to sabotage the construction project.

Or it could be malfunctioning ad-bots (or an AI) that don't realise that the holographic product display isn't working anymore, although the advertising pheromones are.

Once you start to think about the topic, there are loads of possibilities and options.

 

[rinku]

Any of the players got implants? Malfunctioning wafer jack or cybereye could do it.

 

[AndrewW]

Any of the players got implants? Malfunctioning wafer jack or cybereye could do it.

Wouldn't even have to be the players. Could be all those seeing things they report have something in common, like an implant.

 

[Lord High Munchkin]

Time slippage, possibly due to vagary of the time/space continuum "thingie".

Echoes of things past, but no real effects otherwise.

 

[Nidhogg]

Alien, energy based, life form

Yeah that is what I thought of first too. Some form of previously un-encountered alien life form which has a physiology that happens to coincide with what the human psyche associates with haunting. It would be cool to then have them desperately trying to contact the humans to make friends/seek help but having both sides lack the understanding of how to communicate until the players become involved and (hopefully) sort things out.

 

[Fovean]

Pipes or conduits in the walls could be acting as an antenna, picking up normal transmissions on all sorts of frequencies... which of course get modulated by the building materials and sound suitably spooky and all-pervasive.

The modulations cause minor vibration in the piping, which peaks at random times in different places and cause 'bumps in the night' throughout the structure, sometimes sounding like footsteps...

A particularly busy day of transmissions (when the PCs are there of course!) resonate in sub-frequency harmonics, which cause discomfort and queasiness in humans and force any insects and rodents in the area to all make a mass exodus at the same time to escape the painful frequencies... right through the area the PCs are in...

 

[rinku]

Ooh... what about 4D shadows of a higher dimensional creature or phenomenon?

 

[alex_greene]

Ooh... what about 4D shadows of a higher dimensional creature or phenomenon?

One perfect example of a "haunting" that wasn't appeared in the 2000AD series Sinister Dexter, where the "haunting" proved to be a dimensional incursion by forces loyal to one Holy Moses Tannenbaum, from a universe where that monster had not been offed by Messrs Sinister and Dexter and where he was very much alive.

Also, Army of Ghosts from Doctor Who was another excellent example, where the "ghosts" were the footprint, and the "boot" turned out to be five million Cybermen crossing the Void.