I will discuss the potential importance of a dark-sector phase transition in the early universe in setting the measured relic abundance, for a simple scenario with strongly interacting dark matter. Enhancement of the dark matter density within shrinking pockets of the high-temperature phase leads to a dramatic reduction in the late-time dark matter abundance, allowing for much heavier dark matter than in the standard thermal freezeout scenario. I will show new results on a class of specific models realizing this scenario, including experimental constraints and the effects of entropy injection from decay of metastable dark-sector particles.