Learn Swedish: Den maskerade Batman står på taket i det mörka Gotham. - The masked Batman stands on the roof in the dark Gotham.

This is a special rule for proper nouns like names and cities. When you add an adjective to a proper noun, you must use the free definite article (den or det) and the definite adjective form, but the name itself stays in its base form. This is why it is den maskerade Batman instead of den maskerade Batmanen.

How do you know whether to use den or det with names like Batman and Gotham?

Proper nouns referring to people are treated as en-words, so Batman takes the article den. Geographical locations like cities and countries are generally treated as ett-words, which is why Gotham takes det.

Why does maskerade end in -ade here?

Because the phrase is definite (triggered by den), the adjective needs its definite form. Maskerad (masked) is a past participle acting as an adjective. For these adjectives ending in -ad, the definite and plural form is always -ade.

Why does taket get a definite suffix when Batman and Gotham do not?