This article analyzes one manifestation of the supernatural in early modern drama: the admonitory shade. Unlike the ghosts of Elizabethan revenge tragedies—drawn with reference to tragic traditions associated with Seneca and Giraldi Cinzio—the portentous shadow has no former identity, no voice, and no history. But its mere presence communicates a mortal warning, a danger, or a proscription. The pages ahead offer an in-depth analysis of Lope de vega's use of the portentous shadow in six of his plays, spanning from his early triumphs as a playwright in the 1590s to masterpieces of his mature period, notably El caballero de Olmedo. A pattern emerges with respect to this powerful scenic device: drawing on some elemental dramatic effects, Lope attains stunning scenic and emotional results. The striking and ominous shadow that appears to the ill-fated protagonist of El caballero de Olmedo is not, however, a spontaneous, ingenious creation of the playwright. Rather, an examination of the figure through three decades of artistic practice and in relation to literary predecessors reveals it as a dramatic resource that Lope adapted from tradition and fine-tuned through repetition.