Patron-client relationships were of fundamental importance in Nordic medieval society, due to the need for protection and allies. Patron-client bonds were personal and unequal, yet reciprocal. They fulfilled a variety of functions, ranging from the economic to the religious sphere. Because of the scarcity of sources, Iceland is the only area where patron-client bonds can be studied in detail on a local level. There such bonds were termed “friendship” (vinr), but as this term also described horizontal relationships, the boundary between horizontal bonds and patron-client relationships was blurred and changeable. Yet there existed another idiom in the medieval Nordic world for characterizing clients, one in which service was associated with inequality and subordination. This latter form of service was promoted by the Church, and gradually attained more positive connotations. Moreover, with the introduction and spread of writing, vertical relationships became more formalized, as vague obligations were transformed into more circumscribed duties. During the so-called civil wars in the twelfth and the thirteenth centuries, such bonds were increasingly made use of by the monarchy, as they denoted a more hierarchical and formalized relationship than did friendship.