Industrial cities, laboratories, schools, universities, and arcane libraries are all places of learning, and of creation. In places where these forces come together to advance the boundaries of knowledge, ideas fill the heads of the learned like stars in the sky. And in places where there are people with ideas, those people sometimes die before their ideas are brought into the light. Sometimes, when someone with an especially brilliant idea dies, the ides doesn't follow them into the afterlife.
These thoughts persist in our world as Lost Ideas, phantoms of knowledge. Manifesting as nothing more then a shimmer in the air, Lost Ideas seek out those that can bring them to life, and influence their behavior toward that goal. Though incapable of interacting physically with anything, Lost Ideas can subtly change the way that people think, and also plant pieces information in their minds, pushing them toward the end goal of the Idea.
Though not malevolent, Lost Ideas can be formed from any kind of idea. Experiments, devices, enchantments, rituals, and more can come out of the designs of a Lost Idea, and not all of them will be friendly. Lost Ideas themselves don't have a personality or any kind of morality, their sole goal is the completion of the idea they were made of, and they will pursue it to the best of their abilities. Anyone who gets in the way is an obstacle, anyone who helps is tolerated.
Lost Ideas fit into any setting where research or invention takes place. In fantasy games, they would mostly be created around wizard towers or schools. Sci-Fi games with no magic system can explain the Lost Ideas as glitches in computer systems, especially if cybernetics are involved. Steampunk settings are an excellent place for the Ideas, especially in industrial cities or other concentrations of inventors. In modern games, universities are a great place for a Lost Idea to spawn, and if the theme is light-paranormal, a murder mystery is a great place for one.
If you want to make the Lost Idea something that the players are incapable of ignoring, you can add the ability for them to not only influence, but also posses someone who is 'in tune' enough with the idea they represent.
Giving the Lost Idea the power to physically manipulate things also makes it more of a threat, but you may want to apply a limiter. Perhaps only letting it move things that are related to its intellectual domain.
Additional Ideas (2)
Arthur Cross taught engineering and aether sciences at the nations oldest university; Oxford. He was well liked and worked closely with his students on their projects, often involving entire classes in his latest mad idea. But in summer of 1862, he died in a lab accident, much to the dismay of his peers and students. Foul play was, and still is suspected, but nothing has been proven. Since Albert was being uncharacteristically secretive at the time, and whatever he was working on was destroyed in the same incident he was, no one knows exactly what he was working on at the time.
Since about a week after his death, the lab and the area around it has been having problems. Students and faculty alike have blacked out in the area, only to wake up hours later somewhere else with no knowledge of what they were doing. Equipment and materials has gone missing from both public laboratories and private lockers. People have reported having problems with their memory, but can't seem to remember what they have forgotten.
The party can be contacted either or both privately by Valery Cross, daughter of Albert and the one personally experiencing the most incidents, or publicly by the Oxford Administration, primarily by Johnathan Ruskin, head of the engineering department. They are told only about the problems by Ruskin, not the circumstances of Albert's death. Valery will tell them everything with minimal questioning, but makes it clear that she doesn't believe that her father is a ghost.
This part is flexible. The what and how of the device that Albert's Lost Idea is constructing are up to you, but needless to say, it should be incredibly dangerous. Contraptions that bend the laws of physics, or outright ignore them, or devices that will have terrible consequences if even turned on add an element of suspense to the adventure.
The Lost Idea has been building the device in a hidden part of the lab, concealed to the point that the players will not find it at all unless they have read Albert's journal (in his desk in his office), or been told about it by someone who already knows it's there (Valery, or one or two of his students).
Valery knows about the Lost Idea, but thinks that it's the trapped soul of her father, and that helping it is the only way to let him rest. Unless the players can prove to her that it's really just one of his ideas trying to bring itself to life, she will lie and conceal information from them.
The only way to stop the Lost Idea peacefully is to finish the device. After that, the idea will disperse naturally. It actually doesn't even care if you turn it on or not, although you may want to wait a week before smashing the machine to pieces, just to be on the safe side. Destroying the progress that has been made on the machine already will only make the Lost Idea angry, and cause it to entirely abandon the kindness it has previously shown. It will begin possessing people directly, working them until they die, and then finding another labor source. If this isn't stopped within a week, it will learn the ability to possess more then one person at a time.
Players that succeed and manage to do so with no loss of life or limb earn the respect of Albert's students, and his daughter as a permanent contact in the university. Players that don't will just get their paycheck, and be told to leave. Depending on how bad things got, they may even make enemies at Oxford.
Serena Marinez was a brilliant courtier, the kind of mind found only once in a generation. A quick and avid learner of anything she could observe her greatest yearning was for a good intellectual challenge. Regrettably life as a courtier did little to exercise her phenomenal talent, leaving her bored and disdainful of her peers. What little pleasure she derived came from ruminating over what she considered would be a most difficult challenge: to murder every courtier, every lord and lady, and every royalty – an entire coup de tete - and stand completely blameless. The perfect crime. Serena never intended to act upon her musings, simply to entertain herself. The need grew even more pressing after a riding accident left her paralyzed below the waist. Shunning the attentions of well-meaning attendants and bitter over the loss of her independence Serena died slowly in a fevered delirium brought on by infection.
A peculiar string of suspicious accidents seems to plague the palace, brought on by an assassin with intimate knowledge of the court. The delirious thoughts of Serena have begun wafting through the castle, and some have found courtiers with desire to kill. Every murder has been perpetrated by a different courtier, who has no memory of their actions. Each is seemingly flawless, but Serena did not have the benefit of learning from experience so there are consistent mistakes. Additional mistakes are made by those gripped by her ideas, as the ideas can only suggest and not fully elaborate. The great irony is that Serena has become the perfect murderer, how can you suspect someone who is dead?
Someone of importance to the characters has been implicated in the multiple deaths of courtiers which have occurred over the past month. This person stands to be executed soon if someone does not prove his innocence and ferret out the source of the deaths. The real danger of this situation is not realizing the Lost Ideas are about, and sacrificing one innocent for another.