What makes it stranger still is the small oval stone resting inside that hollow, thought to be a pestle, as though someone set it down mid-task and never returned. The boulder, measuring roughly 2.7 metres long and 1.5 metres wide, carries a depression that is almost conical in section, nearly half a metre across and a third of a metre deep. It is the kind of object that rewards a second look.

This is a bullaun stone, a type of ancient carved or worn boulder found across Ireland, typically featuring one or more cup-like hollows whose original purpose remains a matter of debate. Some are associated with early Christian sites, others appear to predate them entirely; many were later absorbed into folk ritual and local devotion. The stone at An Eaglais carries the Irish name Carraig an Aifrinn, meaning roughly "the Mass Rock", which points to a later layer of its history. Mass rocks were outdoor sites used by Catholic communities in Ireland during the Penal era, when the public practice of Catholicism was suppressed and priests celebrated Mass in remote or inconspicuous locations. The local tradition that this bullaun served that function places it within a widespread pattern across Kerry and beyond, where natural features, ancient monuments, and folk memory became quietly entangled over centuries of religious and political pressure.