The most compelling and popular models for dark matter predict that it should congregate and annihilate in stellar cores. Stars where annihilation contributes substantially to the total energy budget look very different to those with which we are familiar. Here I explain the general features of stars modified by dark matter annihilation with the help of a series of grids of 'dark' stellar evolutionary models, and describe the public code with which they were computed. I go on to discuss possible impacts of dark stars on the high-redshift Universe, including the history of reionisation. The preliminary reionisation calculations reproduced here are based on dedicated models for dark star atmospheres, and for the stellar populations to which dark stars would belong.