When conceived rigorously as a literary and cinematic craft, horror is indistinguishable from a singular task: to make an object of the unknown, as the unknown. Only in these terms can its essential accomplishments be estimated.

Horror defines itself through a pact with abstraction, of such primordial compulsion that disciplined metaphysics can only struggle, belatedly, to recapture it. Horror first encounters ‘that’ which philosophy eventually seeks to know.

Lovecraft:
...fear is our deepest and strongest emotion, and the one which best lends itself to the creation of nature-defying illusions. (1/2)

Horror and the unknown or the strange are always closely connected, so that it is hard to create a convincing picture of shattered natural law or cosmic alienage or “outsideness” without laying stress on the emotion of fear. (2/2)

A monster can be no more than a guide, unless it fuses (like Yog Sothoth) into the enveloping extracosmic fabric, as a super-sentient concentration of doors. We can nevertheless avail ourselves of these guides, whose monstrosity says much about the path to the unnameable.

—Nick Land, Abstract Horror
http://www.xenosystems.net/abstract-horror-part-1/