Flying Polyps

As with the image below, Flying Polyps are generally rendered as buoyant, cancerous monstrosities. They live in caverns below the ground, are able to command the winds, and are able to turn invisible at will—though they naturally fade in and out.

In the RPG...

Flying Polyps are highly complex enemies. For a start, they can turn invisible, so can only be targeted with a successful Listen roll, with a Penalty Die applied to the attack. Even when they're not invisible, a Luck roll is needed to simulate their natural phasing in and out. Finally, if your attack is successful, it will only do minimum damage—with 4-point armour also taken off. 

    Their own attacks are just as convoluted. They can attack normally 2D6 times per round because the number of tentacles they have at any time changes, with these attacks ignoring any armour. This means they deal an average of 39 damage per round. Then there's their magic wind powers, of which there are three variations:

    The first—Wind Blast—deals damage equal to the Polyp's damage bonus up to 20 yards. Each 20 yards after that takes off a 1D6. This attack is extremely deadly. Within that first 20 yards, there's a 95% chance of an average Investigator being killed in one hit. Even in the 20-40 yard range, this only drops to 80%.

    Next is the "Fixing Attack", which sucks the victim back towards the Polyp, effectively freezing them in place for a round. This is determined with a STR vs POW opposed roll, which an average Investigator only has a 23% chance of winning—though they get a Bonus Die if 200-1000 yards away. The ability is ineffective beyond that.

    Then finally there's the "Windstorm", wherein multiple Polyps can create a localised hurricane with windspeeds of half the contributing Polyps' expended POW in miles per hour. As an example, say four average Polyps unite and expend all their POW, the storm would have windspeeds of 160mph. Every 20mph above 100 does 1D4 damage to those within it—halved upon a successful Luck roll—so in the example above, an Investigator within the storm would suffer 3D4 damage. Presumably this would be per round, though it doesn't specify. 

    *gasp* I'm exhausted just from summarising. Because so much of this relies on distances, I feel like you would pretty much require a battle map to fight one of these things.

In a video game...

Flying Polyps have actually appeared in a game before—Call of Cthulhu: Dark Corners of the Earth—and were not actually much of a threat because the player coincidentally has a Yithian Lightning Gun by the time they encounter them (I forgot to mention that Polyps are susceptible to heat and electricity).

In a film...

Flying Polyps are taken from the story The Shadow Out of Time, which I think would make for an awesome movie. It not only has the Polyps, but Yithians, globe-trotting adventure, and time-travel (of sorts).