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.