A stack of advertising flyers, printed on coarse cheap paper of various colours -pink, green, buff, or plain white. Sometimes there is a body of text or even photographs printed on the flyers.

SAN Loss - These things start turning up mid-adventure as the SAN losses are starting to rise. At first a single one may be pinned to say a church notice board. Then small piles are on the counters of shops the PCs visit.

They may go unnoticed at first but sooner or later a PC will notice and read one. Then they start seeing them everywhere. On their mat with the post in the morning...in their in tray at work...left on a table in a restaurant they are dining at.... folded as a bookmark in a diary or book they are researching ("I'm certain this wasn't between the pages yesterday...")

The flyers start with disturbing ambiguous messages, which may or may not be related to an event or incident the player has just experienced.
"WE ARE WATCHING" runs the headline on one.
"GUILTY CONSCIENCE?"
"WE KNOW ALL"
"HE IS COMING" may well be a Church tract, but could equally well be taken to refer to the imminent arrival of a mythos being the PCs have started to become aware of.

As time passes the contents of the Flyers become more surreal -photos of dead animals, what appear to be advertisements for everyday items written in hieroglyphics, razors slicing across eyeballs, crippled or deformed children staring blankly (It could be a flyer for a Charity but it seems...wrong) what appear to be blurred photographs or ambiguous descriptions of people or...things...hints at the PCs have seen or done recently...strange symbols, the possibilities are bounded only by the keepers twisted imagination.
The keeper should be careful that these flyers add nothing to the investigation -- they only reflect and amplify the PCs growing fears and insanities. No clues to assist them are to be found in the Flyers dreamlike text and images.

If a PC has a phobia of say...cats...then one morning a handful of flyers showing a picture of a cat with a sardonic knowing expression on its face will be found in his letterbox. Five on the first day, 20 on the second, hundreds scattered like confetti around his garden on the third day...

Questioning the owner of the shop or the driver of the bus, the receptionist at the doctor’s surgery, or the librarian at the University library where these increasingly surreal documents are found will only garner the investigator looks of blank bafflement. No one knows who is leaving these things around, no one can tell where they have been printed...and no one questioned can understand why the PC is making such a fuss about these innocuous advertisements.

As time passes the images and messages should become more ominous and threatening...

A photo of a funeral where the headstone is just visible and may or may not bear a PCs name. A photo of a crime scene...the victim in the chalk outline looks strangely familiar... a photograph of a clawed or webbed hand clutching towards the camera...

The keeper should develop a sliding scale of SAN loss starting with a single point for the first innocuous samples, rising proportionately as the PC becomes more paranoid, and the images and messages on the flyer become ever more disturbing... used judiciously in conjunction with the normal run of the mill shocks to mental equilibrium the ubiquitous presence of these flyers will assist in sending the PC to the very brink…