The Dark Triad consists of three overlapping but distinct personality variables: narcissism, Machiavellianism and psychopathy. To date, however, no research has empirically identified what leads these three variables to overlap or whether other variables share the same core. The present research addresses why and how dark personalities overlap. Drawing from classic work in psychopathy, Hare's Factor 1 or manipulation and callousness were found to be the common antagonistic core. A series of latent variable procedures, including Multisample Structural Equation Models, revealed that for both samples, manipulation and callousness, completely accounted for the associations among the facet scores of the psychopathy, narcissism and Machiavellianism scales. Sample 2 also included Social Dominance Orientation, and results further confirmed that Social Dominance Orientation has the same common core as the Dark Triad. In sum, Hare's Factor 1—manipulation–callousness—emerged as common dark core that accounts for the overlap among antagonistic traits. Copyright © 2012 John Wiley & Sons, Ltd.