This contribution argues that the concept of protean power opens a space to think about the limits of control and knowledge about catastrophic possibilities such as nuclear war. To do so, it offers the first distinctive definition of nuclear luck, which has long been acknowledged by policy and military leaders but remains unaccounted for in scholarship. It further shows that the nuclear realm is defined by two key unknowables. However, it argues that protean power perpetuates a survivability bias which has characterized scholarship so far, before suggesting ways to overcome that bias and modify scholarly ethos to acknowledge such catastrophic possibilities.