In the early years of the 16th-century, Ethiopia's regent, Eleni, sent an ambassador to Portugal to propose an alliance. She sent a man named Mateus. Unfortunately for Mateus, almost nobody believed him.
It's part 7 of the Prester John story, on the trip to Prester John's Ethiopia, and on the Portuguese crown's pursuit of the priest-king and how that story was connected to the developing ones of exploration and colonialism.
This is the first of two episodes on the next jump in the Prester John narrative, as the story pivots to Ethiopia and as Ethiopian envoys and pilgrims travel in 15th-century Italy and Spain.