Recent archaeological fieldwork on Isla de Mona in the Caribbean has led to the discovery of a substantial corpus of early colonial inscriptions inside the darkzone of one of the 200 cave systems on the island. Cave 18, like multiple others on Isla de Mona, was a well-established indigenous spiritual realm in the centuries leading up to European colonization. Christian symbols, individual names, written dates, and Spanish and Latin religious commentaries are located in direct association with preexisting indigenous iconography and activities. This paper applies paleographic (handwriting) analysis to establish the authenticity, authorship, and chronology of the inscriptions and to interpret the nature of this early spiritual encounter. We conclude that these sixteenth-century inscriptions represent visits to the cave by first-generation Europeans, including Spanish royal officials in Puerto Rico, and reflect their reactions to native religious landscapes. The inscriptions on Isla de Mona capture personal, face-to-face encounters with native religion and represent Christian commentaries and reactions to indigenous spaces and worldview in the early colonial period.