The Prester John legend made Europe blind to the reality of foreign lands

Evidence

Its other significance, however, was even more critical. The legend transmuted the world beyond Europe, “the Indies,” into Eurocentric terms. Whatever was the reality of those lands and their peoples, came to be less and less important. For the next 300 years, between the twelfth and the fifteenth centuries, the legend of Prester John provided Europe’s scholars and their less learned coreligionists with a structured and obfuse prism through which the authenticity of every datum, every traveler’s report, every intelligence of its foreign trade, every fable of its poets, and every phatic foible of its soldiery would be screened and strained. — Cedric J. Robinson, Black Marxism_ The Making of the Black…, 516