In recent years, Mixed Reality (MR) headsets have increasingly made advances in terms of capability, affordability and end-user adoption, slowly becoming everyday technology. HCI research typically explores positive aspects of these technologies, focusing on interaction, presence and immersive experiences. However, such technological advances and paradigm shifts often fail to consider the "dark patterns", with potential abusive scenarios, made possible by new technologies (cf. smartphone addiction, social media anxiety disorder). While these topics are getting recent attention in related fields and with the general population, this workshop is aimed at starting an active exploration of abusive, ethical, social and political scenarios of MR research inside the HCI community. With an HCI lens, workshop participants will engage in critical reviews of emerging MR technologies and applications and develop a joint research agenda to address them.