This essay deploys Bruno Latour’s An Inquiry into the Modes of Existence and Bert States’s Great Reckonings in Little Rooms to analyze the pyrotechnics used in mystery plays to symbolize supernatural truths. On the one hand, these effects cultivated aesthetic immersion, allowing audiences to perceive stage illusions as real. On the other hand, they drew attention to their own artfulness, inviting spectators to marvel at human achievement and contemplate the possibility of misfire. This paradox encapsulates the theological ambiguities of medieval religious theater, which asked spectators to suspend disbelief in the name of conversion even as they maintained skepticism about sacred simulacra. Latour’s metaphysics allows us to see how mystery plays deployed multiple modes of existence, each of which mediated the others but could not reduce or explain them. States’s theater phenomenology shows us how mystery plays used self-given realities like flame to shuttle between human and nonhuman standpoints. If Latour rejects phenomenology for its refusal to consider the agency of the nonhuman, States’s focus on reality as resistance offers an implicit retort. I propose a rapprochement by showing that theater phenomenologists and medieval effects masters are both willing to embrace the ontological work of nonhuman actants.