I would like to run False Hydra but in Call of Cthulhu.
A False Hydra is a creature with a skill to erase someone from everyone's memory after devouring them, what's more, it can be seen only in mirrors or when it stops singing (when it sings and you are within its range, you are hallucinating and can't see trails of blood, holes in buildings, etc.).
The climate fits perfectly and the story can be adjusted to the system without a problem, but I have one concern – Is there a Lovecraftian creature which is anyhow similar or at least some spells in the rulebook that can cause False Hydra effects, or should I just homebrew this creature?
From what I know the False Hydra is not canon in D&D as well, but I would like to know if there is anything similar in CoC.
Best Answer
Not knowing the creature or the source adventure you are referencing:
It is cthulhu, so as soon as you think "is this possible?" you are mistaken the basic idea of lovecraftian horror. Most of the entities he described were merely a perception of an otherwise nonmaterialistic otherworldly beings, that cannot be perceived by normal mortal senses in their original form.
If your Creature chooses to appear vaguely like a hydra, it may as well choose to do so. On the other hand you may as well play with the sanity of your PCs and have them dream about that image, so that they may be expecting something similar, which in of itself might warp their perception of it.
Since Call of Cthulu can be played with few to no dice rolls at all (I hope you do not plan to have your mortals fight the hydra) it is pretty much irrelevant how it looks, as long as your players are frightened.