Here is an interesting plot seed somebody posted on the RPG.net forums.

Derek Lindley is an amusing "Debunker" of the Mythos. He goes around and more or less does his best to cover up tales of psychic ability, ghosts, and destroy cults using financial or social means as much as old fashioned firepower. His goal as a real magician is to protect people from the truth that would end the world.

The Keeper privately informs Derek's player that the character is unknowingly one of the Thousand Masks of Nyarlathotep But he doesn't know that he is.

Derek will meet up with Randolf Carter at one point in the campaign and learns that he won't able to choose death as an escape because he will just revert to his 'true' form.

The more his Mythos lore gies up, the more Derek becomes "aware" of his true nature.

A possible ending of the campaign is when Derek allows himself to be "re-absorbed" into the God in order to re-seal the dimensional instability he is causing.

Plot Twist: one of the other (non)-player characters who is his lover is unknowingly carries his child.

End the campaign with the visual of a fetus wrapped up in a tentacle with the unborn child developing a gruesome smile.