A World War One castaway drifts onto a vast tract of foul black land newly risen from the Pacific floor. There he finds an ancient monolith carved with marine and near-human figures, and watches a colossal, vaguely man-shaped creature rise from the water to worship before it.
Written in 1917, "Dagon" is the earliest story to crystallise the imagery that would define the Cthulhu Mythos: civilisations beneath the sea, hybrid aquatic beings, and monuments to indifferent gods. The Deep Ones and R'lyeh both trace their roots to this brief tale.