This is the 12472nd most frequent Swedish word.
skräckserien
"The horror series."
Here, 'skräckserien' is used as a definite noun (the horror series) to specify a particular series related to the genre of horror.
Skräckserien jag såg igår var riktigt spännande.
The horror series I watched yesterday was really thrilling.
In this instance, 'skräckserien' is used in reference to a freshly released horror series, aiding in conveying newness or current relevance.
Har du hört talas om den nya skräckserien på TV?
Have you heard about the new horror series on TV?
Here, 'skräckserier' is used in the plural form to refer generically to multiple horror series without specifying particular ones.