The Northern Crusades came to an end not with the formal conversion of Lithuania but with the victory of Poland and Lithuania over the Teutonic Knights at the battle of Grunwald in 1410. This victory made possible the conversion of Samogitia and, by the 1440s, the final neutralisation of paganism as a political force in the Baltic. However, the Ottoman conquest of Constantinople intensified curiosity about non-Christian religions and peoples from beyond the edges of Christendom and coincided with the rise of a new humanist ethnography grounded in curiosity about human nature as well as a desire to convert people to Christianity. This chapter examines the responses of the fifteenth-century humanist project to the apparent survival of pockets of pre-Christian religion from Vilnius to Tenerife, paying attention to the ways in which this discourse anticipated debates that would follow European voyages to the New World. The chapter considers the unique contribution of Pawel Wlodkowic in arguing for the rights of unchristianised peoples and assesses the reliability of humanist ethnographies as a source for pre-Christian religions. The chapter argues that ‘mere Christianisation’, a surface identification with Christianity, was often enough in this period for a region to be assimilated to Christendom.