Splinters of Daoloth

Those who enter the Sacred Light (an avatar of Daoloth) become aware that it is a living, alien presence. At first, the person experiences euphoria, but as the subject’s mind fills with knowledge, terror follows as this knowledge mounts and mounts, becoming too much for their mind to bear. Unless finding some way to stop the process, the acquisition of cosmic truths may turn this person into a Splinter of Daoloth.

In the RPG...

Splinters of Daoloth do not speak, and move slowly. Their sole purpose is to touch the forehead of someone so that they can share the "gift of truth", which is sanity-blasting. If the Investigator could survive the Sanity roll, it could be beneficial gaining the 1D10 Cthulhu Mythos that comes with it. That stuff is hard to come by. If reaching zero Sanity, the victim has a 60% chance of becoming a Splinter themselves.
    Being human, their stats mostly reflect that, though their STR, INT, and POW do get pumped up to 100.

In a video game...

Because they are slow, and nothing more than human, Splinters would only really be a threat to players if they could sneak up on someone and surprise them. Their biggest threat comes from the fact that they would be driving NPCs insane, and 3-in-5 of those will then become Splinters, and spread like a kind of zombie virus.

In a film...

As I alluded to above, I feel like Splinters have a lot in common with zombies, being that they're slow and can spread their "infection" to make more Splinters, so in that regard, I think they would make for an interesting twist on the genre. Instead of killing people, they're instead driving them insane.