Terrors from Beyond

Terrors from Beyond—also known as Astral Parasites—appear like jellyfish floating through the air... when they can be seen. Normally they occupy their own dimension, completely invisible to ours, but with special devices, they can be seen. The only problem is, as soon as we can see them, they can also see us... and they are always hungry.

In the RPG...

Terrors from Beyond can only attack—and be attacked by—those who can see them. Though not mentioned in the 7e Malleus Monstrorum, the old edition and the original story—From Beyond—state that victims can be taken back to the Terrors' own dimension, leaving behind nothing but their clothes and effects. In a strange twist, only certain spells that cause physical damage can affect them. All others automatically fail.

    The old Malleus Monstrorum gave Terrors from Beyond no STR, CON, DEX, or SIZ, as they were intangible until they attacked, whereas the 7e edition has given these stats, and indicates that the creatures become solid as soon as they are sensed. They were intangible in the original story, so I'm not sure how I feel about this deviation. I think I like them being incorporeal until the moment they strike.

In a video game...

I think the Terrors from Beyond would be pretty cool in a video game. Perhaps the player comes across a Tillinghast Resonator and foolishly switches it on. Like the source story—From Beyond—seeing the creatures floating around and through you would seem cool... until they attack.

In a film...

There have been a few adaptation of From Beyond, including the wildly off-track Stuart Gordon version, but I feel like the central premise could also be used to great effect in a serious horror film.