Considering the high attrition rate of investigators in Call of Cthulhu, it is amazing that there are enough new investigators to fill the ranks. In truth, investigators have been guided to their calling by the Nephilim for ages: a hint left here, a tome left there, or perhaps even a friendship with a Nephilim incarnate. The Nephilim are the true guardians of the Earth, seeking to stave off the increased presence of the Black Moon, that has been caused by the nuclear testing instigated by the Templars in their mad quest for power. Horrors were unleashed that made even the Selenim seem benevolent by comparison. Now the stars are right, but for whom?
For humans (and thus Nephilim):
For monsters:
POW drain and POW costs become Ka costs; MP costs become Ch'awe costs. Nephilim do not suffer from any phenomenon similar to SAN loss, as they are considered monsters in Call of Cthulhu. Mythos spells now require Ch'awe and Ka, not MP and POW; an enterprising GM may require a dominant Ka or Solar-Ka threshold to cast such spells. Nephilim may or may not be able to create analogs of Mythos magic using sorcery, summoning, or alchemy; if not, they must rely on any simulacrum skills to cast Mythos spells.
The astrological signs and portents reveal that a particularly nasty Moon-Ka plexus will occur underwater a few kilometers (miles) off the coast of an isolated coastal town called Innsmouth. If the Nephilim character does not want to reveal the actual reason for visiting the town, perhaps the investigator group needs a vacation; what better place than a quiet seaside town, far from the worries of the city?
Upon arrival, the investigators may find the natives somewhat cold and unfriendly, for they are unused to visitors. All will no doubt seem fine at first, but the team will soon discover the presence of the Men in Black and perhaps the Deep Ones...
Consider the possibility that the Men in Black are actually the minions of the Templars. Though the Templars in the area are few in number, they have gained powerful allies. A generation ago they made a pact with the Selenim of the Sea nearby, who may or may not be recognized as Deep Ones by the investigators. Periodically the Men in Black will kidnap and brainwash one of the locals, perhaps planting a false memory of being abducted by a UFO; they will then turn over the person to the Deep Ones for their amphibious simulacrum breeding program. The Deep Ones gain assistance in their goal of creating a simulacrum equally at home on land as in the water, while the Templars are provided with magical assistance not normally accessable to their kind.
Another possibility is that the Men in Black are a ruse by the Templars to draw in an investigator team in order to capture them, and harvest the magic of any Nephilim members. One nasty twist would be for there actually to be a Deep One colony nearby, and have them invade the town while the investigators are being held, forcing the Templars to release them so that they may together combat the Selenim menace. The Templars are treacherous, so the investigators had better be prepared to make their escape.
Or, perhaps it turns out to be a quiet vacation, as nothing becomes of the Moon-Ka plexus. Maybe that astrological lore roll was a fumble after all. Time enough to research a few neglected skills.
The above originally appeared in The Chaosium Digest, volumes 10.3 and 11.3.