Can somebody please explain why nouns like "the Devil", "the Pope", "the Holy Spirit" need the word "the"?

Aren’t they all proper nouns and therefore supposed to not need the definite article?

In Portuguese you put the equivalent of 'the" in front of people’s names. (A Michelle or O Robert)

In some Catalan dialects you use a special determinate article just for people (en Robert, na Michelle), one for “common” things there could be many of (sa house, es car) and a third for things there’s only one of (el Pope, la Reina).

Languages are fun!