Not sure if you have any of these but here are a few of my favourites that I think thematically fit the atmosphere of Darkest Dungeon. I condensed some of the longer ones.
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We live on a placid island of ignorance in the midst of black seas of infinity, and it was not meant that we should voyage far.

The most merciful thing in the world, I think, is the inability of the human mind to correlate all its contents.

That is not dead which can eternal lie, And with strange aeons even death may die.

I cannot even hint what it was like, for it was a compound of all that is unclean, uncanny, unwelcome, abnormal, and detestable.

It was the ghoulish shade of decay, antiquity, and desolation; the putrid, dripping eidolon of unwholesome revelation; the awful baring of that which the merciful earth should always hide.

God knows it was not of this world—or no longer of this world—yet to my horror I saw in its eaten-away and bone-revealing outlines a leering, abhorrent travesty on the human shape.

Who knows the end? What has risen may sink, and what has sunk may rise. Loathsomeness waits and dreams in the deep, and decay spreads over the tottering cities of men.

Mankind was not absolutely alone among the conscious things of earth, for shapes came out of the dark to visit the faithful few.

I have looked upon all that the universe has to hold of horror, and even the skies of spring and the flowers of summer must ever afterward be poison to me.

It is absolutely necessary that some of earth’s dark, dead corners and unplumbed depths be let alone; lest sleeping abnormalities wake to resurgent life, and blasphemously surviving nightmares squirm and splash out of their black lairs to newer and wider conquests.

It was the unusual number and fame of these predecessors which made our own expedition—ample though it was—so little noticed by the world at large.

What we did see—for the mists were indeed all too malignly thinned—was something altogether different, and immeasurably more hideous and detestable.

We shall see these things, and other things which no breathing creature has yet seen.