In the Twilight

At least ten empires rose and fell during the Meridian of Earth. Each was glorious and wrested such secrets from the universe as to enable it to bend laws of nature obdurate to earlier cultures to its whim. Each in time fell into decadence, dwindled, and died, but at the end of the Meridian Time, the Earth had been transformed by their works; it had become the abode of beings other than Man.

As the Twilight fell and the sun grew bloated and sanguine, those Outsiders and abhuman things encroached ever closer on the nations of Man. By and by, they gained greater dominion over the Earth. In the early centuries, the technologies of the elder Meridian still functioned, and Man comprehended enough to build great walls as a defense against the inhuman. As Twilight deepened, many of these redoubts fell, but a few stood fast and managed even to throw back their foe. The Coming Night was held in abeyance for so long that generations passed and many began to doubt it would ever fall.

But beyond the walls, the Great Beasts crouched and waited with patience inhuman but not infinity, and abhuman armies gathered in the deepening in gloom...

Here's the pitch: Take the early modern bleakness, occasional black humor, and body-warping chaos of Warhammer Fantasy and put it in a Dying Earth gone weird like Hodgson's The Night Land, making sure to filter the Watchers (Great Beasts in this case) through Lovecraftiania, a hint of kaiju, and good old fashion goetic demonology. Wrap it all in "points of light" surrounded by walls out of Attack on Titan.