This article examines an obscure custom found in Iberian ethnography: that of having one's eldest children serve as godparents for their own youngest siblings, starting with the seventh. The paper's main working hypothesis is that this custom is to be understood in the context of underlying conceptions that fairytales convey in a symbolical guise. The argument highlights the relationship of examined notions with the "Dragon Slayer" theme, to bring out stable themata concerning ontological complexity and metamorphosis, in the light of which the Iberian custom is interpreted.The primary subject matter of this paper is an obscure custom that I found in western Iberia in the 1980s: that of choosing one's eldest children to serve as godparents for their own youngest siblings, starting with the seventh. At the time, this custom attracted my attention because it seemed to shun the possibility of using the idiom of spiritual kinship, as is commonly done in southern Europe, to promote and renew social ties across households within small communities. Indeed, I will argue that this particular custom is to be understood from an altogether different angle: that of fundamental concepts of a metaphysical sort, which inform the behaviour of flesh and blood people in their daily lives. In this article, I propose to make sense of such concepts on their own terms. One important means for this task is the tracing of symbolic redundancy on different levels of cultural life, such as social practices (think of so-called customs and rites), everyday notions (such as so-called beliefs or superstitions), and narrative folklore (such as fairytales). This entails the heuristic hypothesis that use of, say, fairytales is of help in explaining the behaviour of actual people in traditional settings. Such is, indeed, one strong assumption underlying my present attempt to generalise from an obscure custom, which seemed to me intractable at first, to a theoretical model. Moreover, I assume that the tracing of symbolic redundancy entails a comparative stance-for it takes a consideration of the endless variability of folklore on a pan-European scale to grasp its stable themata.