Question on Cthulhu

[Doomsy]

I almost always drop the 'i' out of Yithians when typing it, and I have no idea why.

The corebook has a few pieces of Yithian technology in it too, if I remember right, but all of the species mentioned have their own entry. The Elder Things tend to use biotech for the most part so their technology might actually be somewhat alive and would probably have had to have been in stasis or hibernating since the Elder Things bowed out. Yithian technology is built to last forever and their mastery over time can make it show up almost anywhere.

About the only issues you might have with them is that the Elder Things seem to show up very rarely in most modules or books so getting a lot of fluff on them can be hard, and the Yithians are probably the closest thing CoC has to 'benevolent' mythos creatures in that they are not particularly hostile to mankind and usually leave their subjects alive.

And as for how scary technology can be?

Shoggoths are Elder Thing technology.