This chapter analyzes the political incorporation from below of a frontier kingdom: Navarre. Different historians have pointed out the importance of royal agents in the process of conquest and assimilation of frontier territories from a top-down perspective of the processes of political incorporation centered on the Crown. Despite the obvious value of such an approach, it tells us very little about how the processes of political incorporation worked on the ground. This chapter aims to achieve this by analyzing the incorporation of Navarre from Rena’s vantage point. During the 13 years (1512–1525) he spent in this frontier kingdom, Rena acted as a perfect agent on behalf of the Crown, and as such he became a key figure in Navarrese politics. Rena’s contribution to the incorporation of Navarre went beyond his role implementing the orders from the imperial court. He also helped to define the privileged position of this frontier kingdom in the network of polities making up the Spanish empire, and also in the reshaping of Navarrese society after its conquest. In so doing, he contributed to the work of incorporating this frontier kingdom from below.