From the late 19th century to today, legislatures have been present in 80% of dictatorships. How legislatures affect outcomes in authoritarian regimes, and why they exist in the first place are central puzzles in research on authoritarian politics. A prominent argument holds that authoritarian legislatures are instruments of power-sharing which constrain dictators while allowing them to co-opt elites as well as potential opponents. Therefore, legislatures serve the function of stabilizing autocratic rule. In contrast, we argue that under certain conditions legislatures have the opposite effect. When autocratic rule co-exists with powerful ethnoreligious cleavages, the presence of an elected legislature can have destabilizing effects if inclusion is selective and reinforces the exclusion of specific ethno-religious groups. Excluded groups are in fact more likely to respond to elected legislatures with an escalation of terrorism and violent conflict. We test this argument with new data on terrorism by ethnic and ethno-religious groups in autocracies (1970-2016). By explicitly examining the ethno-political context of authoritarian regimes and legislatures, we demonstrate that legislatures, if not carefully designed, can worsen political violence in autocracies and ultimately undermine a dictator’s survival in office.