I am unsure whether to class H.P Lovecraft as a horror writer or not, but one thing I can say is: his imagery and creations of an ‘other’ last a long time after you’ve read his work. As an example of this point: note Cthulhu in today’s society.
This short tale was written in 1929 and the whole story has a sense of hovering: the town, nature, the townspeople (the people of Dunwich’s accents are phonetically spelt out to give the reader a sense of their closed off lifestyle) and even the ‘things’ that are older from other planes of existence but want to enter ours to destroy it. This itself seems to be the plot for ‘The Dunwich Horror’. It is a hovering, a waiting, that seems to build, as good horror writing should. Within this tale is an unseen horror that is biding its time, or using a particular family in order to find the time to take apart the earth for its own motivations, whatever they may be. The family this tale centres on, the Whateleys, are written in just as vague a way as the invisible threats themselves, but with such eeriness that what is unknown is much more fearsome than what could be spelled out in description. But when descriptions are placed within this story: watch out! They are vivid indeed!
And while allusions to ancient languages and cults may be a general feature of generic horror, I enjoyed the fact that Lovecraft pushes beyond what is known. He does not just write about what is in this world; but creates enemies to humanity that go beyond even what our universe seems able to contain. And this is where Lovecraft creates amazing horror: his horrific elements go beyond the boundaries of the earth into planes of existence that are cosmic and therefore more terrifying as it shows how truly small and almost useless people are against such ‘things’.
Check out ‘The Weird’ edited by Ann and Jeff Vandermeer for this short story and others in the same field of weird and terrifying.