"The Dark Eidolon" is a sword and sorcery short story by American writer Clark Ashton Smith, forming part of his Zothique cycle of stories. It was first published in Weird Tales in 1935 and has been variously republished, notably in the anthology The Spell of Seven, edited by L. Sprague de Camp. Described by de Camp in his introduction to the story as 'one of the most horrible' of Smith's tales, it chronicles the life and death of the dread sorcerer Namirrha.