Which "the" article do you use if there is no noun?
There is a video game called "The Long Dark."
Would the article change depending on the word, even without a noun?
The title is "The long dark". The word "dark" has to be a noun because otherwise the expression would be incomplete (the long dark .. what???).
I would translate it: Das lange Dunkel.
(Which means something like "the long period of darkness").
If "dark" were a adjective, it would have to be followed by a noun, for example: The long dark night.
This would be: Die lange dunkle Nacht.
If the word were the noun "darkness", then I would translate it as "Dunkelheit": Die lange Dunkelheit.
"Die Dunkelheit" is much more common than "das Dunkel". The latter sounds more poetic and mysterious.