Religion makes great material for horror stories. It wrestles with the same mysteries as that genre does — death, the soul, the nature of evil. It traffics in awe, which is a closely related emotion to terror. Catholicism, with its richness of symbols and incense-perfumed ritual, has been a staple of scary fiction right up through Fox’s current iteration of “The Exorcist.”

HBO’s “The Young Pope,” beginning on Sunday and showing Sundays and Mondays, is a visually sublime but textually ridiculous horror tale in which the monster is the pontiff himself.

This 10-episode series begins after the election as pope of Lenny Belardo (Jude Law), a fresh-faced, little-known American. The church establishment, led by the Vatican secretary of state, Cardinal Voiello (Silvio Orlando), hopes he will be “a telegenic puppet” and a bridge between church conservatives and liberals. Cardinal Belardo chooses the name Pius XIII.

For the complacent cardinals, XIII proves to be an unlucky number. The new pope is, superficially, novel: He’s hooked on Cherry Coke Zero, he’s pop-culture literate, he — well, he looks like Jude Law. But his beliefs turn out to be militantly conservative, if not medieval.