Horror tests setting numbers

I have found a few snips about Horror checks, and Sanity Mental Attacks.
But no definite rule section.

Figure that I have just missed it. As it was always a big part of CoC.

If there are some pages that cover it you know of please pass them along.

From the bits I have found it looks like a Will + Resilience with Successes 1 to 5 as normal.

It almost feels like it might be better as an opposed roll against the level of Horror and the setting.
That way th GM can add effects like Pericing, Vicious, or even Persistent.
Being able to add effects gives more options than just giving it a high number of Successes needed.

Or perhaps assign a Horror Rating to a creature.
It rolls that many d6 with effects.
The PC rolls test, Will + Res, Difficulty 0, for every Success it blocks one Damage, Courage blocks as normal.
Then effects like Piercing, Vicious, Drain, all still have effects.
I can see an uncanny valley Horror that has Persistent.
It is not that it was truly more horrible, but so close to human but not the mind will not let go and just keeps replaying it.

Just making sure I did not miss something, as it feels like it , and have the RAW more or less correct.

Thank for help all.

Most of the monsters in the GM Guide have the Fearsome quality, as well as a basic mental attack.

Fearsome X quality forces the players to pass a Will+Resilience test at difficulty X the first time they see the monster or receive stress from the basic mental attack of that monster. The monster can also use their mental attack against the PCs whenever he wants.