We describe here a pattern of archaeological sites that suggest that ‘mainland’ Aboriginal people were viewed by their Torres Strait neighbours as being specialists in particular ritual knowledge. The region under consideration includes the northern-most tip of the Australian continent and extends northward through Torres Strait to Papua. Our study area focuses on the southern end of the region: the Australian mainland as well as Pabaju (Albany Island), Muri (Mt Adolphus Island) and associated islands and islets. Archaeological investigation over many years reveals a high density of ritual sites over this relatively small area. These include sites on prominent headlands. The density and visibility of sites could be interpreted as both marking and ‘marketing’ ritual expertise. The location of some of the sites also suggests they served as ‘sentinels’ within a cosmo-political seascape. Far from having an impoverished role in regional exchange networks, Australian mainlanders clearly held something of extraordinary value that drew people from the Torres Strait to their shores. We contend that southern reciprocity in regional trade and exchange may have been based on intangible knowledge transactions, in particular, knowledge related to increase ritual.