Clotton is a fictional town invented by Ramsey Campbell in his "Dunwich Horror" pastiche, "The Horror From the Bridge", published in his 1964 collection The Inhabitant of the Lake. It is part of his Severn Valley milieu.
In that story, Clotton is described as a small town located where the river Ton flows into the Severn. Only a "few leaning red-brick houses... remain of the uptown section of the once-prosperous town"; the rest of the town was deliberately destroyed in 1931, for reasons explained in the story. In "The Horror Under Warrendown," a later Campbell story, Clotton is mentioned as "a small settlement which appeared to be largely abandoned, its few occupied houses huddling together on each side of a river." The story notes the town's "stagnant almost reptilian smell and chilly haze."
The town's most noteworthy feature, also dating to 1931, is a "20-foot high concrete building...on the bank of the Ton", with an "eldritch sign clumsily engraved on each wall", carvings that "were blurred by moss and weather."
The town was once home to James Phipps, "a gaunt pallid-faced man, with jet-black hair, and long bony hands" who died in 1898, aged well over a century, and his son Lionel Phipps (1806-1931). Both were odd individuals given to "unorthodox scientific researches" and nocturnal excavation. They lived on Riverside Alley, "a little-tenanted street within sight of a bridge over the Ton".
Outside of Clotton, according to "The Horror From the Bridge", there is a "pit on a patch of waste ground on what used to be Canning Road, near the river," containing "roughly-cut steps, each carrying a carven five-pointed sign, which led down into abysmal darkness."
In "The Franklyn Paragraphs", which mentions Clotton as a place visited by the cult led by Roland Franklyn, Franklyn's widow notes that "we went down the steps below Clotton."